diff --git a/Documentation/cmd-stream-events.txt b/Documentation/cmd-stream-events.txt
index 72a9c21..37af110 100644
--- a/Documentation/cmd-stream-events.txt
+++ b/Documentation/cmd-stream-events.txt
@@ -90,6 +90,16 @@
 eventCreatedOn:: Time in seconds since the UNIX epoch when this event was
 created.
 
+== Change Deleted
+
+Sent when a change has been deleted.
+
+type:: "change-deleted"
+
+change:: link:json.html#change[change attribute]
+
+deleter:: link:json.html#account[account attribute]
+
 === Change Merged
 
 Sent when a change has been merged into the git repository.
diff --git a/Documentation/config-project-config.txt b/Documentation/config-project-config.txt
index cc5386f..4456484 100644
--- a/Documentation/config-project-config.txt
+++ b/Documentation/config-project-config.txt
@@ -186,9 +186,10 @@
 +
 Controls whether server-side signed push validation is required on the
 project. Only has an effect if signed push validation is enabled on the
-server, and link:#receive.enableSignedPush is set on the project. See
-the link:config-gerrit.html#receive.enableSignedPush[global
-configuration] for details.
+server, and link:#receive.enableSignedPush[`receive.enableSignedPush`] is
+set on the project. See the
+link:config-gerrit.html#receive.enableSignedPush[global configuration]
+for details.
 +
 Default is `INHERIT`, which means that this property is inherited from
 the parent project.
diff --git a/Documentation/rest-api-accounts.txt b/Documentation/rest-api-accounts.txt
index e28a9c4..de5f278 100644
--- a/Documentation/rest-api-accounts.txt
+++ b/Documentation/rest-api-accounts.txt
@@ -1098,10 +1098,7 @@
 .Response
 ----
   HTTP/1.1 200 OK
-  Content-Disposition: attachment
-  Content-Type: application/json; charset=UTF-8
 
-  )]}'
   ok
 ----
 
@@ -1805,6 +1802,69 @@
   ]
 ----
 
+[delete-draft-comments]
+=== Delete Draft Comments
+--
+'POST /accounts/link:#account-id[\{account-id\}]/drafts:delete'
+--
+
+Deletes some or all of a user's draft comments. The set of comments to delete is
+specified as a link:#delete-draft-comments-input[DeleteDraftCommentsInput]
+entity. An empty input entity deletes all comments.
+
+Only drafts belonging to the caller may be deleted.
+
+.Request
+----
+  POST /accounts/self/drafts.delete HTTP/1.0
+  Content-Type: application/json; charset=UTF-8
+
+  {
+    "query": "is:abandoned"
+  }
+----
+
+As a response, a list of
+link:#deleted-draft-comment-info[DeletedDraftCommentInfo] entities is returned.
+
+.Response
+----
+  HTTP/1.1 200 OK
+  Content-Disposition: attachment
+  Content-Type: application/json; charset=UTF-8
+
+   )]}'
+   [
+     {
+       "change": {
+         "id": "myProject~master~I8473b95934b5732ac55d26311a706c9c2bde9940",
+         "project": "myProject",
+         "branch": "master",
+         "change_id": "I8473b95934b5732ac55d26311a706c9c2bde9940",
+         "subject": "Implementing Feature X",
+         "status": "ABANDONED",
+         "created": "2013-02-01 09:59:32.126000000",
+         "updated": "2013-02-21 11:16:36.775000000",
+         "insertions": 34,
+         "deletions": 101,
+         "_number": 3965,
+         "owner": {
+           "name": "John Doe"
+         }
+       },
+       "deleted": [
+         {
+           "id": "TvcXrmjM",
+           "path": "gerrit-server/src/main/java/com/google/gerrit/server/project/RefControl.java",
+           "line": 23,
+           "message": "[nit] trailing whitespace",
+           "updated": "2013-02-26 15:40:43.986000000"
+         }
+       ]
+     }
+   ]
+----
+
 [[sign-contributor-agreement]]
 === Sign Contributor Agreement
 --
@@ -2316,6 +2376,37 @@
 |`name`                     |The name of the agreement.
 |=================================
 
+[[delete-draft-comments-input]]
+=== DeleteDraftCommentsInput
+The `DeleteDraftCommentsInput` entity contains information specifying a set of
+draft comments that should be deleted.
+
+[options="header",cols="1,^1,5"]
+|=================================
+|Field Name                 ||Description
+|`query`                    |optional|
+A link:user-search.html[change query] limiting results to changes matching this
+query; `has:draft` is implied and not necessary to list explicitly. If not set,
+matches all changes with drafts.
+|=================================
+
+[[deleted-draft-comment-info]]
+=== DeletedDraftCommentInfo
+The `DeletedDraftCommentInfo` entity contains information about draft comments
+that were deleted.
+
+[options="header",cols="1,6"]
+|=================================
+|Field Name                 |Description
+|`change`                   |
+link:rest-api-changes.html#change-info[ChangeInfo] entity describing the change
+on which one or more comments was deleted. Populated with only the
+link:rest-api-changes.html#skip_mergeable[SKIP_MERGEABLE] option.
+|`deleted`                  |
+List of link:rest-api-changes.html#comment-info[CommentInfo] entities for each
+comment that was deleted.
+|=================================
+
 [[diff-preferences-info]]
 === DiffPreferencesInfo
 The `DiffPreferencesInfo` entity contains information about the diff
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/FormatUtil.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/FormatUtil.java
index 38e1b60..c8d052e 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/FormatUtil.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/FormatUtil.java
@@ -126,25 +126,7 @@
     if (size == 0) {
       return Resources.C.notAvailable();
     }
-    int p = Math.abs(saturatedCast(delta * 100 / size));
-    return p + "%";
-  }
-
-  /**
-   * Returns the {@code int} nearest in value to {@code value}.
-   *
-   * @param value any {@code long} value
-   * @return the same value cast to {@code int} if it is in the range of the {@code int} type,
-   *     {@link Integer#MAX_VALUE} if it is too large, or {@link Integer#MIN_VALUE} if it is too
-   *     small
-   */
-  private static int saturatedCast(long value) {
-    if (value > Integer.MAX_VALUE) {
-      return Integer.MAX_VALUE;
-    }
-    if (value < Integer.MIN_VALUE) {
-      return Integer.MIN_VALUE;
-    }
-    return (int) value;
+    long percentage = Math.abs(Math.round(delta * 100.0 / size));
+    return percentage + "%";
   }
 }
diff --git a/java/com/google/gerrit/acceptance/AccountCreator.java b/java/com/google/gerrit/acceptance/AccountCreator.java
index 1416797..69492a9 100644
--- a/java/com/google/gerrit/acceptance/AccountCreator.java
+++ b/java/com/google/gerrit/acceptance/AccountCreator.java
@@ -16,6 +16,7 @@
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Sets;
 import com.google.gerrit.common.Nullable;
@@ -150,6 +151,10 @@
     accounts.values().removeIf(a -> ids.contains(a.id));
   }
 
+  public ImmutableList<TestAccount> getAll() {
+    return ImmutableList.copyOf(accounts.values());
+  }
+
   private void addGroupMember(AccountGroup.UUID groupUuid, Account.Id accountId)
       throws OrmException, IOException, NoSuchGroupException, ConfigInvalidException {
     InternalGroupUpdate groupUpdate =
diff --git a/java/com/google/gerrit/acceptance/EventRecorder.java b/java/com/google/gerrit/acceptance/EventRecorder.java
index 5654c35..1af71b8 100644
--- a/java/com/google/gerrit/acceptance/EventRecorder.java
+++ b/java/com/google/gerrit/acceptance/EventRecorder.java
@@ -25,6 +25,7 @@
 import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.data.RefUpdateAttribute;
+import com.google.gerrit.server.events.ChangeDeletedEvent;
 import com.google.gerrit.server.events.ChangeMergedEvent;
 import com.google.gerrit.server.events.Event;
 import com.google.gerrit.server.events.RefEvent;
@@ -69,6 +70,8 @@
               public void onEvent(Event e) {
                 if (e instanceof ReviewerDeletedEvent) {
                   recordedEvents.put(ReviewerDeletedEvent.TYPE, (ReviewerDeletedEvent) e);
+                } else if (e instanceof ChangeDeletedEvent) {
+                  recordedEvents.put(ChangeDeletedEvent.TYPE, (ChangeDeletedEvent) e);
                 } else if (e instanceof RefEvent) {
                   RefEvent event = (RefEvent) e;
                   String key =
@@ -138,6 +141,21 @@
     return events;
   }
 
+  private ImmutableList<ChangeDeletedEvent> getChangeDeletedEvents(int expectedSize) {
+    String key = ChangeDeletedEvent.TYPE;
+    if (expectedSize == 0) {
+      assertThat(recordedEvents).doesNotContainKey(key);
+      return ImmutableList.of();
+    }
+    assertThat(recordedEvents).containsKey(key);
+    ImmutableList<ChangeDeletedEvent> events =
+        FluentIterable.from(recordedEvents.get(key))
+            .transform(ChangeDeletedEvent.class::cast)
+            .toList();
+    assertThat(events).hasSize(expectedSize);
+    return events;
+  }
+
   public void assertNoRefUpdatedEvents(String project, String branch) throws Exception {
     getRefUpdatedEvents(project, branch, 0);
   }
@@ -197,6 +215,18 @@
     }
   }
 
+  public void assertChangeDeletedEvents(String... expected) {
+    ImmutableList<ChangeDeletedEvent> events = getChangeDeletedEvents(expected.length / 2);
+    int i = 0;
+    for (ChangeDeletedEvent event : events) {
+      String id = event.change.get().id;
+      assertThat(id).isEqualTo(expected[i]);
+      String reviewer = event.deleter.get().email;
+      assertThat(reviewer).isEqualTo(expected[i + 1]);
+      i += 2;
+    }
+  }
+
   public void close() {
     eventListenerRegistration.remove();
   }
diff --git a/java/com/google/gerrit/extensions/api/accounts/AccountApi.java b/java/com/google/gerrit/extensions/api/accounts/AccountApi.java
index 6adc978..b7fce5f 100644
--- a/java/com/google/gerrit/extensions/api/accounts/AccountApi.java
+++ b/java/com/google/gerrit/extensions/api/accounts/AccountApi.java
@@ -109,6 +109,9 @@
 
   void deleteExternalIds(List<String> externalIds) throws RestApiException;
 
+  List<DeletedDraftCommentInfo> deleteDraftComments(DeleteDraftCommentsInput input)
+      throws RestApiException;
+
   /**
    * A default implementation which allows source compatibility when adding new methods to the
    * interface.
@@ -301,5 +304,11 @@
     public void deleteExternalIds(List<String> externalIds) throws RestApiException {
       throw new NotImplementedException();
     }
+
+    @Override
+    public List<DeletedDraftCommentInfo> deleteDraftComments(DeleteDraftCommentsInput input)
+        throws RestApiException {
+      throw new NotImplementedException();
+    }
   }
 }
diff --git a/java/com/google/gerrit/extensions/api/accounts/DeleteDraftCommentsInput.java b/java/com/google/gerrit/extensions/api/accounts/DeleteDraftCommentsInput.java
new file mode 100644
index 0000000..113f3d4
--- /dev/null
+++ b/java/com/google/gerrit/extensions/api/accounts/DeleteDraftCommentsInput.java
@@ -0,0 +1,35 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.extensions.api.accounts;
+
+import com.google.gerrit.common.Nullable;
+import com.google.gerrit.extensions.restapi.DefaultInput;
+
+public class DeleteDraftCommentsInput {
+  /**
+   * Delete comments only on changes that match this query.
+   *
+   * <p>If null or empty, delete comments on all changes.
+   */
+  @DefaultInput public String query;
+
+  public DeleteDraftCommentsInput() {
+    this(null);
+  }
+
+  public DeleteDraftCommentsInput(@Nullable String query) {
+    this.query = query;
+  }
+}
diff --git a/java/com/google/gerrit/extensions/api/accounts/DeletedDraftCommentInfo.java b/java/com/google/gerrit/extensions/api/accounts/DeletedDraftCommentInfo.java
new file mode 100644
index 0000000..c15d5bc
--- /dev/null
+++ b/java/com/google/gerrit/extensions/api/accounts/DeletedDraftCommentInfo.java
@@ -0,0 +1,24 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.extensions.api.accounts;
+
+import com.google.gerrit.extensions.common.ChangeInfo;
+import com.google.gerrit.extensions.common.CommentInfo;
+import java.util.List;
+
+public class DeletedDraftCommentInfo {
+  public ChangeInfo change;
+  public List<CommentInfo> deleted;
+}
diff --git a/java/com/google/gerrit/extensions/events/ChangeDeletedListener.java b/java/com/google/gerrit/extensions/events/ChangeDeletedListener.java
new file mode 100644
index 0000000..70014f3
--- /dev/null
+++ b/java/com/google/gerrit/extensions/events/ChangeDeletedListener.java
@@ -0,0 +1,25 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.extensions.events;
+
+import com.google.gerrit.extensions.annotations.ExtensionPoint;
+
+/** Notified whenever a Change is deleted. */
+@ExtensionPoint
+public interface ChangeDeletedListener {
+  interface Event extends ChangeEvent {}
+
+  void onChangeDeleted(Event event);
+}
diff --git a/java/com/google/gerrit/httpd/WebModule.java b/java/com/google/gerrit/httpd/WebModule.java
index 538d605..d115f43 100644
--- a/java/com/google/gerrit/httpd/WebModule.java
+++ b/java/com/google/gerrit/httpd/WebModule.java
@@ -56,7 +56,9 @@
     installAuthModule();
     if (options.enableMasterFeatures()) {
       install(new UrlModule(options, authConfig));
-      install(new UiRpcModule());
+      if (options.enableGwtUi()) {
+        install(new UiRpcModule());
+      }
     }
     install(new GerritRequestModule());
     install(new GitOverHttpServlet.Module(options.enableMasterFeatures()));
diff --git a/java/com/google/gerrit/server/api/accounts/AccountApiImpl.java b/java/com/google/gerrit/server/api/accounts/AccountApiImpl.java
index 9ef5753..15e21fe 100644
--- a/java/com/google/gerrit/server/api/accounts/AccountApiImpl.java
+++ b/java/com/google/gerrit/server/api/accounts/AccountApiImpl.java
@@ -20,6 +20,8 @@
 import com.google.gerrit.common.RawInputUtil;
 import com.google.gerrit.extensions.api.accounts.AccountApi;
 import com.google.gerrit.extensions.api.accounts.AgreementInput;
+import com.google.gerrit.extensions.api.accounts.DeleteDraftCommentsInput;
+import com.google.gerrit.extensions.api.accounts.DeletedDraftCommentInfo;
 import com.google.gerrit.extensions.api.accounts.EmailApi;
 import com.google.gerrit.extensions.api.accounts.EmailInput;
 import com.google.gerrit.extensions.api.accounts.GpgKeyApi;
@@ -51,6 +53,7 @@
 import com.google.gerrit.server.restapi.account.AddSshKey;
 import com.google.gerrit.server.restapi.account.CreateEmail;
 import com.google.gerrit.server.restapi.account.DeleteActive;
+import com.google.gerrit.server.restapi.account.DeleteDraftComments;
 import com.google.gerrit.server.restapi.account.DeleteEmail;
 import com.google.gerrit.server.restapi.account.DeleteExternalIds;
 import com.google.gerrit.server.restapi.account.DeleteSshKey;
@@ -125,6 +128,7 @@
   private final Index index;
   private final GetExternalIds getExternalIds;
   private final DeleteExternalIds deleteExternalIds;
+  private final DeleteDraftComments deleteDraftComments;
   private final PutStatus putStatus;
   private final GetGroups getGroups;
   private final EmailApiImpl.Factory emailApi;
@@ -165,6 +169,7 @@
       Index index,
       GetExternalIds getExternalIds,
       DeleteExternalIds deleteExternalIds,
+      DeleteDraftComments deleteDraftComments,
       PutStatus putStatus,
       GetGroups getGroups,
       EmailApiImpl.Factory emailApi,
@@ -204,6 +209,7 @@
     this.index = index;
     this.getExternalIds = getExternalIds;
     this.deleteExternalIds = deleteExternalIds;
+    this.deleteDraftComments = deleteDraftComments;
     this.putStatus = putStatus;
     this.getGroups = getGroups;
     this.emailApi = emailApi;
@@ -561,4 +567,14 @@
       throw asRestApiException("Cannot delete external IDs", e);
     }
   }
+
+  @Override
+  public List<DeletedDraftCommentInfo> deleteDraftComments(DeleteDraftCommentsInput input)
+      throws RestApiException {
+    try {
+      return deleteDraftComments.apply(account, input);
+    } catch (Exception e) {
+      throw asRestApiException("Cannot delete draft comments", e);
+    }
+  }
 }
diff --git a/java/com/google/gerrit/server/config/GerritGlobalModule.java b/java/com/google/gerrit/server/config/GerritGlobalModule.java
index 0761d2e..4c043b6 100644
--- a/java/com/google/gerrit/server/config/GerritGlobalModule.java
+++ b/java/com/google/gerrit/server/config/GerritGlobalModule.java
@@ -33,6 +33,7 @@
 import com.google.gerrit.extensions.events.AgreementSignupListener;
 import com.google.gerrit.extensions.events.AssigneeChangedListener;
 import com.google.gerrit.extensions.events.ChangeAbandonedListener;
+import com.google.gerrit.extensions.events.ChangeDeletedListener;
 import com.google.gerrit.extensions.events.ChangeIndexedListener;
 import com.google.gerrit.extensions.events.ChangeMergedListener;
 import com.google.gerrit.extensions.events.ChangeRestoredListener;
@@ -311,6 +312,7 @@
     DynamicSet.setOf(binder(), GitReferenceUpdatedListener.class);
     DynamicSet.setOf(binder(), AssigneeChangedListener.class);
     DynamicSet.setOf(binder(), ChangeAbandonedListener.class);
+    DynamicSet.setOf(binder(), ChangeDeletedListener.class);
     DynamicSet.setOf(binder(), CommentAddedListener.class);
     DynamicSet.setOf(binder(), HashtagsEditedListener.class);
     DynamicSet.setOf(binder(), ChangeMergedListener.class);
diff --git a/java/com/google/gerrit/server/events/ChangeDeletedEvent.java b/java/com/google/gerrit/server/events/ChangeDeletedEvent.java
new file mode 100644
index 0000000..63142fd
--- /dev/null
+++ b/java/com/google/gerrit/server/events/ChangeDeletedEvent.java
@@ -0,0 +1,28 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.events;
+
+import com.google.common.base.Supplier;
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.server.data.AccountAttribute;
+
+public class ChangeDeletedEvent extends ChangeEvent {
+  public static final String TYPE = "change-deleted";
+  public Supplier<AccountAttribute> deleter;
+
+  public ChangeDeletedEvent(Change change) {
+    super(TYPE, change);
+  }
+}
diff --git a/java/com/google/gerrit/server/events/EventTypes.java b/java/com/google/gerrit/server/events/EventTypes.java
index cd2b464..5498ec8 100644
--- a/java/com/google/gerrit/server/events/EventTypes.java
+++ b/java/com/google/gerrit/server/events/EventTypes.java
@@ -24,6 +24,7 @@
   static {
     register(AssigneeChangedEvent.TYPE, AssigneeChangedEvent.class);
     register(ChangeAbandonedEvent.TYPE, ChangeAbandonedEvent.class);
+    register(ChangeDeletedEvent.TYPE, ChangeDeletedEvent.class);
     register(ChangeMergedEvent.TYPE, ChangeMergedEvent.class);
     register(ChangeRestoredEvent.TYPE, ChangeRestoredEvent.class);
     register(CommentAddedEvent.TYPE, CommentAddedEvent.class);
diff --git a/java/com/google/gerrit/server/events/StreamEventsApiListener.java b/java/com/google/gerrit/server/events/StreamEventsApiListener.java
index 367a38b..97a3f39 100644
--- a/java/com/google/gerrit/server/events/StreamEventsApiListener.java
+++ b/java/com/google/gerrit/server/events/StreamEventsApiListener.java
@@ -26,6 +26,7 @@
 import com.google.gerrit.extensions.common.RevisionInfo;
 import com.google.gerrit.extensions.events.AssigneeChangedListener;
 import com.google.gerrit.extensions.events.ChangeAbandonedListener;
+import com.google.gerrit.extensions.events.ChangeDeletedListener;
 import com.google.gerrit.extensions.events.ChangeMergedListener;
 import com.google.gerrit.extensions.events.ChangeRestoredListener;
 import com.google.gerrit.extensions.events.CommentAddedListener;
@@ -75,6 +76,7 @@
 public class StreamEventsApiListener
     implements AssigneeChangedListener,
         ChangeAbandonedListener,
+        ChangeDeletedListener,
         ChangeMergedListener,
         ChangeRestoredListener,
         WorkInProgressStateChangedListener,
@@ -95,6 +97,7 @@
     protected void configure() {
       DynamicSet.bind(binder(), AssigneeChangedListener.class).to(StreamEventsApiListener.class);
       DynamicSet.bind(binder(), ChangeAbandonedListener.class).to(StreamEventsApiListener.class);
+      DynamicSet.bind(binder(), ChangeDeletedListener.class).to(StreamEventsApiListener.class);
       DynamicSet.bind(binder(), ChangeMergedListener.class).to(StreamEventsApiListener.class);
       DynamicSet.bind(binder(), ChangeRestoredListener.class).to(StreamEventsApiListener.class);
       DynamicSet.bind(binder(), CommentAddedListener.class).to(StreamEventsApiListener.class);
@@ -522,4 +525,20 @@
       logger.atSevere().withCause(e).log("Failed to dispatch event");
     }
   }
+
+  @Override
+  public void onChangeDeleted(ChangeDeletedListener.Event ev) {
+    try {
+      ChangeNotes notes = getNotes(ev.getChange());
+      Change change = notes.getChange();
+      ChangeDeletedEvent event = new ChangeDeletedEvent(change);
+
+      event.change = changeAttributeSupplier(change, notes);
+      event.deleter = accountAttributeSupplier(ev.getWho());
+
+      dispatcher.get().postEvent(change, event);
+    } catch (OrmException | PermissionBackendException e) {
+      logger.atSevere().withCause(e).log("Failed to dispatch event");
+    }
+  }
 }
diff --git a/java/com/google/gerrit/server/extensions/events/ChangeDeleted.java b/java/com/google/gerrit/server/extensions/events/ChangeDeleted.java
new file mode 100644
index 0000000..dd1dc07
--- /dev/null
+++ b/java/com/google/gerrit/server/extensions/events/ChangeDeleted.java
@@ -0,0 +1,66 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.extensions.events;
+
+import com.google.common.flogger.FluentLogger;
+import com.google.gerrit.extensions.api.changes.NotifyHandling;
+import com.google.gerrit.extensions.common.AccountInfo;
+import com.google.gerrit.extensions.common.ChangeInfo;
+import com.google.gerrit.extensions.events.ChangeDeletedListener;
+import com.google.gerrit.extensions.registration.DynamicSet;
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.server.account.AccountState;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import com.google.inject.Singleton;
+import java.sql.Timestamp;
+
+@Singleton
+public class ChangeDeleted {
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+
+  private final DynamicSet<ChangeDeletedListener> listeners;
+  private final EventUtil util;
+
+  @Inject
+  ChangeDeleted(DynamicSet<ChangeDeletedListener> listeners, EventUtil util) {
+    this.listeners = listeners;
+    this.util = util;
+  }
+
+  public void fire(Change change, AccountState deleter, Timestamp when) {
+    if (!listeners.iterator().hasNext()) {
+      return;
+    }
+    try {
+      Event event = new Event(util.changeInfo(change), util.accountInfo(deleter), when);
+      for (ChangeDeletedListener l : listeners) {
+        try {
+          l.onChangeDeleted(event);
+        } catch (Exception e) {
+          util.logEventListenerError(this, l, e);
+        }
+      }
+    } catch (OrmException e) {
+      logger.atSevere().withCause(e).log("Couldn't fire event");
+    }
+  }
+
+  private static class Event extends AbstractChangeEvent implements ChangeDeletedListener.Event {
+    Event(ChangeInfo change, AccountInfo deleter, Timestamp when) {
+      super(change, deleter, when, NotifyHandling.ALL);
+    }
+  }
+}
diff --git a/java/com/google/gerrit/server/permissions/ProjectControl.java b/java/com/google/gerrit/server/permissions/ProjectControl.java
index 4a4ea37..46bf45f 100644
--- a/java/com/google/gerrit/server/permissions/ProjectControl.java
+++ b/java/com/google/gerrit/server/permissions/ProjectControl.java
@@ -98,23 +98,6 @@
     state = ps;
   }
 
-  ProjectControl forUser(CurrentUser who) {
-    ProjectControl r =
-        new ProjectControl(
-            uploadGroups,
-            receiveGroups,
-            permissionFilter,
-            changeControlFactory,
-            permissionBackend,
-            refFilterFactory,
-            identifiedUserFactory,
-            who,
-            state);
-    // Not per-user, and reusing saves lookup time.
-    r.allSections = allSections;
-    return r;
-  }
-
   ForProject asForProject() {
     return new ForProjectImpl();
   }
diff --git a/java/com/google/gerrit/server/permissions/RefControl.java b/java/com/google/gerrit/server/permissions/RefControl.java
index 762dfbe..b324e77 100644
--- a/java/com/google/gerrit/server/permissions/RefControl.java
+++ b/java/com/google/gerrit/server/permissions/RefControl.java
@@ -77,14 +77,6 @@
     return projectControl.getUser();
   }
 
-  RefControl forUser(CurrentUser who) {
-    ProjectControl newCtl = projectControl.forUser(who);
-    if (relevant.isUserSpecific()) {
-      return newCtl.controlForRef(refName);
-    }
-    return new RefControl(identifiedUserFactory, newCtl, refName, relevant);
-  }
-
   /** Is this user a ref owner? */
   boolean isOwner() {
     if (owner == null) {
diff --git a/java/com/google/gerrit/server/query/change/ChangeData.java b/java/com/google/gerrit/server/query/change/ChangeData.java
index 1813211..7fb0989 100644
--- a/java/com/google/gerrit/server/query/change/ChangeData.java
+++ b/java/com/google/gerrit/server/query/change/ChangeData.java
@@ -1089,14 +1089,15 @@
   public boolean isReviewedBy(Account.Id accountId) throws OrmException {
     Collection<String> stars = stars(accountId);
 
-    if (stars.contains(
-        StarredChangesUtil.REVIEWED_LABEL + "/" + currentPatchSet().getPatchSetId())) {
-      return true;
-    }
+    PatchSet ps = currentPatchSet();
+    if (ps != null) {
+      if (stars.contains(StarredChangesUtil.REVIEWED_LABEL + "/" + ps.getPatchSetId())) {
+        return true;
+      }
 
-    if (stars.contains(
-        StarredChangesUtil.UNREVIEWED_LABEL + "/" + currentPatchSet().getPatchSetId())) {
-      return false;
+      if (stars.contains(StarredChangesUtil.UNREVIEWED_LABEL + "/" + ps.getPatchSetId())) {
+        return false;
+      }
     }
 
     return reviewedBy().contains(accountId);
diff --git a/java/com/google/gerrit/server/restapi/account/DeleteDraftComments.java b/java/com/google/gerrit/server/restapi/account/DeleteDraftComments.java
new file mode 100644
index 0000000..26d6cf4
--- /dev/null
+++ b/java/com/google/gerrit/server/restapi/account/DeleteDraftComments.java
@@ -0,0 +1,211 @@
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.restapi.account;
+
+import static com.google.common.collect.ImmutableList.toImmutableList;
+import static com.google.gerrit.server.CommentsUtil.setCommentRevId;
+
+import com.google.common.base.CharMatcher;
+import com.google.common.base.Strings;
+import com.google.common.collect.ImmutableList;
+import com.google.gerrit.common.Nullable;
+import com.google.gerrit.common.TimeUtil;
+import com.google.gerrit.extensions.api.accounts.DeleteDraftCommentsInput;
+import com.google.gerrit.extensions.api.accounts.DeletedDraftCommentInfo;
+import com.google.gerrit.extensions.client.ListChangesOption;
+import com.google.gerrit.extensions.common.CommentInfo;
+import com.google.gerrit.extensions.restapi.AuthException;
+import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.extensions.restapi.RestApiException;
+import com.google.gerrit.extensions.restapi.RestModifyView;
+import com.google.gerrit.index.query.Predicate;
+import com.google.gerrit.index.query.QueryParseException;
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.Account.Id;
+import com.google.gerrit.reviewdb.client.Comment;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.reviewdb.client.Project;
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.CommentsUtil;
+import com.google.gerrit.server.CurrentUser;
+import com.google.gerrit.server.PatchSetUtil;
+import com.google.gerrit.server.account.AccountResource;
+import com.google.gerrit.server.change.ChangeJson;
+import com.google.gerrit.server.patch.PatchListCache;
+import com.google.gerrit.server.patch.PatchListNotAvailableException;
+import com.google.gerrit.server.permissions.PermissionBackendException;
+import com.google.gerrit.server.query.change.ChangeData;
+import com.google.gerrit.server.query.change.ChangeQueryBuilder;
+import com.google.gerrit.server.query.change.HasDraftByPredicate;
+import com.google.gerrit.server.query.change.InternalChangeQuery;
+import com.google.gerrit.server.restapi.change.CommentJson;
+import com.google.gerrit.server.restapi.change.CommentJson.CommentFormatter;
+import com.google.gerrit.server.update.BatchUpdate;
+import com.google.gerrit.server.update.BatchUpdate.Factory;
+import com.google.gerrit.server.update.BatchUpdateListener;
+import com.google.gerrit.server.update.BatchUpdateOp;
+import com.google.gerrit.server.update.ChangeContext;
+import com.google.gerrit.server.update.UpdateException;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import com.google.inject.Singleton;
+import java.sql.Timestamp;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+@Singleton
+public class DeleteDraftComments
+    implements RestModifyView<AccountResource, DeleteDraftCommentsInput> {
+
+  private final Provider<ReviewDb> db;
+  private final Provider<CurrentUser> userProvider;
+  private final BatchUpdate.Factory batchUpdateFactory;
+  private final Provider<ChangeQueryBuilder> queryBuilderProvider;
+  private final Provider<InternalChangeQuery> queryProvider;
+  private final ChangeData.Factory changeDataFactory;
+  private final ChangeJson.Factory changeJsonFactory;
+  private final Provider<CommentJson> commentJsonProvider;
+  private final CommentsUtil commentsUtil;
+  private final PatchSetUtil psUtil;
+  private final PatchListCache patchListCache;
+
+  @Inject
+  DeleteDraftComments(
+      Provider<ReviewDb> db,
+      Provider<CurrentUser> userProvider,
+      Factory batchUpdateFactory,
+      Provider<ChangeQueryBuilder> queryBuilderProvider,
+      Provider<InternalChangeQuery> queryProvider,
+      ChangeData.Factory changeDataFactory,
+      ChangeJson.Factory changeJsonFactory,
+      Provider<CommentJson> commentJsonProvider,
+      CommentsUtil commentsUtil,
+      PatchSetUtil psUtil,
+      PatchListCache patchListCache) {
+    this.db = db;
+    this.userProvider = userProvider;
+    this.batchUpdateFactory = batchUpdateFactory;
+    this.queryBuilderProvider = queryBuilderProvider;
+    this.queryProvider = queryProvider;
+    this.changeDataFactory = changeDataFactory;
+    this.changeJsonFactory = changeJsonFactory;
+    this.commentJsonProvider = commentJsonProvider;
+    this.commentsUtil = commentsUtil;
+    this.psUtil = psUtil;
+    this.patchListCache = patchListCache;
+  }
+
+  @Override
+  public ImmutableList<DeletedDraftCommentInfo> apply(
+      AccountResource rsrc, DeleteDraftCommentsInput input)
+      throws RestApiException, OrmException, UpdateException {
+    CurrentUser user = userProvider.get();
+    if (!user.isIdentifiedUser()) {
+      throw new AuthException("Authentication required");
+    }
+    if (!rsrc.getUser().hasSameAccountId(user)) {
+      // Disallow even for admins or users with Modify Account. Drafts are not like preferences or
+      // other account info; there is no way even for admins to read or delete another user's drafts
+      // using the normal draft endpoints under the change resource, so disallow it here as well.
+      // (Admins may still call this endpoint with impersonation, but in that case it would pass the
+      // hasSameAccountId check.)
+      throw new AuthException("Cannot delete drafts of other user");
+    }
+
+    CommentFormatter commentFormatter = commentJsonProvider.get().newCommentFormatter();
+    Account.Id accountId = rsrc.getUser().getAccountId();
+    Timestamp now = TimeUtil.nowTs();
+    Map<Project.NameKey, BatchUpdate> updates = new LinkedHashMap<>();
+    List<Op> ops = new ArrayList<>();
+    for (ChangeData cd :
+        queryProvider
+            .get()
+            // Don't attempt to mutate any changes the user can't currently see.
+            .enforceVisibility(true)
+            .query(predicate(accountId, input))) {
+      BatchUpdate update =
+          updates.computeIfAbsent(
+              cd.project(), p -> batchUpdateFactory.create(db.get(), p, rsrc.getUser(), now));
+      Op op = new Op(commentFormatter, accountId);
+      update.addOp(cd.getId(), op);
+      ops.add(op);
+    }
+
+    // Currently there's no way to let some updates succeed even if others fail. Even if there were,
+    // all updates from this operation only happen in All-Users and thus are fully atomic, so
+    // allowing partial failure would have little value.
+    batchUpdateFactory.execute(updates.values(), BatchUpdateListener.NONE, false);
+
+    return ops.stream().map(Op::getResult).filter(Objects::nonNull).collect(toImmutableList());
+  }
+
+  private Predicate<ChangeData> predicate(Account.Id accountId, DeleteDraftCommentsInput input)
+      throws BadRequestException {
+    Predicate<ChangeData> hasDraft = new HasDraftByPredicate(accountId);
+    if (CharMatcher.whitespace().trimFrom(Strings.nullToEmpty(input.query)).isEmpty()) {
+      return hasDraft;
+    }
+    try {
+      return Predicate.and(hasDraft, queryBuilderProvider.get().parse(input.query));
+    } catch (QueryParseException e) {
+      throw new BadRequestException("Invalid query: " + e.getMessage(), e);
+    }
+  }
+
+  private class Op implements BatchUpdateOp {
+    private final CommentFormatter commentFormatter;
+    private final Account.Id accountId;
+    private DeletedDraftCommentInfo result;
+
+    Op(CommentFormatter commentFormatter, Id accountId) {
+      this.commentFormatter = commentFormatter;
+      this.accountId = accountId;
+    }
+
+    @Override
+    public boolean updateChange(ChangeContext ctx)
+        throws OrmException, PatchListNotAvailableException, PermissionBackendException {
+      ImmutableList.Builder<CommentInfo> comments = ImmutableList.builder();
+      boolean dirty = false;
+      for (Comment c : commentsUtil.draftByChangeAuthor(ctx.getDb(), ctx.getNotes(), accountId)) {
+        dirty = true;
+        PatchSet.Id psId = new PatchSet.Id(ctx.getChange().getId(), c.key.patchSetId);
+        setCommentRevId(
+            c, patchListCache, ctx.getChange(), psUtil.get(ctx.getDb(), ctx.getNotes(), psId));
+        commentsUtil.deleteComments(ctx.getDb(), ctx.getUpdate(psId), Collections.singleton(c));
+        comments.add(commentFormatter.format(c));
+      }
+      if (dirty) {
+        result = new DeletedDraftCommentInfo();
+        result.change =
+            changeJsonFactory
+                .create(ListChangesOption.SKIP_MERGEABLE)
+                .format(changeDataFactory.create(ctx.getDb(), ctx.getNotes()));
+        result.deleted = comments.build();
+      }
+      return dirty;
+    }
+
+    @Nullable
+    DeletedDraftCommentInfo getResult() {
+      return result;
+    }
+  }
+}
diff --git a/java/com/google/gerrit/server/restapi/account/GetCapabilities.java b/java/com/google/gerrit/server/restapi/account/GetCapabilities.java
index 5c466bf..7889f6e 100644
--- a/java/com/google/gerrit/server/restapi/account/GetCapabilities.java
+++ b/java/com/google/gerrit/server/restapi/account/GetCapabilities.java
@@ -26,8 +26,8 @@
 import com.google.gerrit.extensions.api.access.PluginPermission;
 import com.google.gerrit.extensions.config.CapabilityDefinition;
 import com.google.gerrit.extensions.registration.DynamicMap;
+import com.google.gerrit.extensions.restapi.BinaryResult;
 import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
-import com.google.gerrit.extensions.restapi.Response;
 import com.google.gerrit.extensions.restapi.RestApiException;
 import com.google.gerrit.extensions.restapi.RestReadView;
 import com.google.gerrit.server.CurrentUser;
@@ -172,9 +172,9 @@
     }
 
     @Override
-    public Response<String> apply(Capability resource) throws ResourceNotFoundException {
+    public BinaryResult apply(Capability resource) throws ResourceNotFoundException {
       permissionBackend.checkUsesDefaultCapabilities();
-      return Response.ok("ok");
+      return BinaryResult.create("ok\n");
     }
   }
 }
diff --git a/java/com/google/gerrit/server/restapi/account/Module.java b/java/com/google/gerrit/server/restapi/account/Module.java
index be0924a..9b012f7 100644
--- a/java/com/google/gerrit/server/restapi/account/Module.java
+++ b/java/com/google/gerrit/server/restapi/account/Module.java
@@ -107,6 +107,8 @@
     get(ACCOUNT_KIND, "external.ids").to(GetExternalIds.class);
     post(ACCOUNT_KIND, "external.ids:delete").to(DeleteExternalIds.class);
 
+    post(ACCOUNT_KIND, "drafts:delete").to(DeleteDraftComments.class);
+
     // The gpgkeys REST endpoints are bound via GpgApiModule.
 
     factory(AccountsUpdate.Factory.class);
diff --git a/java/com/google/gerrit/server/restapi/change/CommentJson.java b/java/com/google/gerrit/server/restapi/change/CommentJson.java
index a562592..7112bbf 100644
--- a/java/com/google/gerrit/server/restapi/change/CommentJson.java
+++ b/java/com/google/gerrit/server/restapi/change/CommentJson.java
@@ -41,7 +41,7 @@
 import java.util.Map;
 import java.util.TreeMap;
 
-class CommentJson {
+public class CommentJson {
 
   private final AccountLoader.Factory accountLoaderFactory;
 
@@ -161,7 +161,7 @@
     }
   }
 
-  class CommentFormatter extends BaseCommentFormatter<Comment, CommentInfo> {
+  public class CommentFormatter extends BaseCommentFormatter<Comment, CommentInfo> {
     @Override
     protected CommentInfo toInfo(Comment c, AccountLoader loader) {
       CommentInfo ci = new CommentInfo();
diff --git a/java/com/google/gerrit/server/restapi/change/DeleteChangeOp.java b/java/com/google/gerrit/server/restapi/change/DeleteChangeOp.java
index 9658fb4..d41e504 100644
--- a/java/com/google/gerrit/server/restapi/change/DeleteChangeOp.java
+++ b/java/com/google/gerrit/server/restapi/change/DeleteChangeOp.java
@@ -26,6 +26,7 @@
 import com.google.gerrit.server.PatchSetUtil;
 import com.google.gerrit.server.StarredChangesUtil;
 import com.google.gerrit.server.change.AccountPatchReviewStore;
+import com.google.gerrit.server.extensions.events.ChangeDeleted;
 import com.google.gerrit.server.project.NoSuchChangeException;
 import com.google.gerrit.server.update.BatchUpdateOp;
 import com.google.gerrit.server.update.BatchUpdateReviewDb;
@@ -45,6 +46,7 @@
   private final PatchSetUtil psUtil;
   private final StarredChangesUtil starredChangesUtil;
   private final DynamicItem<AccountPatchReviewStore> accountPatchReviewStore;
+  private final ChangeDeleted changeDeleted;
 
   private Change.Id id;
 
@@ -52,10 +54,12 @@
   DeleteChangeOp(
       PatchSetUtil psUtil,
       StarredChangesUtil starredChangesUtil,
-      DynamicItem<AccountPatchReviewStore> accountPatchReviewStore) {
+      DynamicItem<AccountPatchReviewStore> accountPatchReviewStore,
+      ChangeDeleted changeDeleted) {
     this.psUtil = psUtil;
     this.starredChangesUtil = starredChangesUtil;
     this.accountPatchReviewStore = accountPatchReviewStore;
+    this.changeDeleted = changeDeleted;
   }
 
   @Override
@@ -75,6 +79,7 @@
     deleteChangeElementsFromDb(ctx, id);
 
     ctx.deleteChange();
+    changeDeleted.fire(ctx.getChange(), ctx.getAccount(), ctx.getWhen());
     return true;
   }
 
diff --git a/javatests/com/google/gerrit/acceptance/api/accounts/AccountIT.java b/javatests/com/google/gerrit/acceptance/api/accounts/AccountIT.java
index de66b87..1eaadca 100644
--- a/javatests/com/google/gerrit/acceptance/api/accounts/AccountIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/accounts/AccountIT.java
@@ -15,8 +15,10 @@
 package com.google.gerrit.acceptance.api.accounts;
 
 import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.common.truth.Truth.assertWithMessage;
+import static com.google.common.truth.Truth.assert_;
 import static com.google.common.truth.Truth8.assertThat;
 import static com.google.gerrit.acceptance.GitUtil.deleteRef;
 import static com.google.gerrit.acceptance.GitUtil.fetch;
@@ -62,8 +64,11 @@
 import com.google.gerrit.common.data.Permission;
 import com.google.gerrit.common.data.PermissionRule.Action;
 import com.google.gerrit.extensions.api.accounts.AccountInput;
+import com.google.gerrit.extensions.api.accounts.DeleteDraftCommentsInput;
+import com.google.gerrit.extensions.api.accounts.DeletedDraftCommentInfo;
 import com.google.gerrit.extensions.api.accounts.EmailInput;
 import com.google.gerrit.extensions.api.changes.AddReviewerInput;
+import com.google.gerrit.extensions.api.changes.DraftInput;
 import com.google.gerrit.extensions.api.changes.ReviewInput;
 import com.google.gerrit.extensions.api.changes.StarsInput;
 import com.google.gerrit.extensions.api.config.ConsistencyCheckInfo;
@@ -73,6 +78,7 @@
 import com.google.gerrit.extensions.common.AccountDetailInfo;
 import com.google.gerrit.extensions.common.AccountInfo;
 import com.google.gerrit.extensions.common.ChangeInfo;
+import com.google.gerrit.extensions.common.CommentInfo;
 import com.google.gerrit.extensions.common.EmailInfo;
 import com.google.gerrit.extensions.common.GpgKeyInfo;
 import com.google.gerrit.extensions.common.GroupInfo;
@@ -92,6 +98,7 @@
 import com.google.gerrit.gpg.testing.TestKey;
 import com.google.gerrit.mail.Address;
 import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.Branch;
 import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.reviewdb.client.RefNames;
@@ -2583,6 +2590,160 @@
     assertThat(stalenessChecker.isStale(accountId)).isFalse();
   }
 
+  @Test
+  public void deleteAllDraftComments() throws Exception {
+    try {
+      TestTimeUtil.resetWithClockStep(1, SECONDS);
+      Project.NameKey project2 = createProject("project2");
+      PushOneCommit.Result r1 = createChange();
+
+      TestRepository<?> tr2 = cloneProject(project2);
+      PushOneCommit.Result r2 =
+          createChange(
+              tr2,
+              "refs/heads/master",
+              "Change in project2",
+              PushOneCommit.FILE_NAME,
+              "content2",
+              null);
+
+      // Create 2 drafts each on both changes for user.
+      setApiUser(user);
+      createDraft(r1, PushOneCommit.FILE_NAME, "draft 1a");
+      createDraft(r1, PushOneCommit.FILE_NAME, "draft 1b");
+      createDraft(r2, PushOneCommit.FILE_NAME, "draft 2a");
+      createDraft(r2, PushOneCommit.FILE_NAME, "draft 2b");
+      assertThat(gApi.changes().id(r1.getChangeId()).current().draftsAsList()).hasSize(2);
+      assertThat(gApi.changes().id(r2.getChangeId()).current().draftsAsList()).hasSize(2);
+
+      // Create 1 draft on first change for admin.
+      setApiUser(admin);
+      createDraft(r1, PushOneCommit.FILE_NAME, "admin draft");
+      assertThat(gApi.changes().id(r1.getChangeId()).current().draftsAsList()).hasSize(1);
+
+      // Delete user's draft comments; leave admin's alone.
+      setApiUser(user);
+      List<DeletedDraftCommentInfo> result =
+          gApi.accounts().self().deleteDraftComments(new DeleteDraftCommentsInput());
+
+      // Results are ordered according to the change search, most recently updated first.
+      assertThat(result).hasSize(2);
+      DeletedDraftCommentInfo del2 = result.get(0);
+      assertThat(del2.change.changeId).isEqualTo(r2.getChangeId());
+      assertThat(del2.deleted.stream().map(c -> c.message)).containsExactly("draft 2a", "draft 2b");
+      DeletedDraftCommentInfo del1 = result.get(1);
+      assertThat(del1.change.changeId).isEqualTo(r1.getChangeId());
+      assertThat(del1.deleted.stream().map(c -> c.message)).containsExactly("draft 1a", "draft 1b");
+
+      assertThat(gApi.changes().id(r1.getChangeId()).current().draftsAsList()).isEmpty();
+      assertThat(gApi.changes().id(r2.getChangeId()).current().draftsAsList()).isEmpty();
+
+      setApiUser(admin);
+      assertThat(gApi.changes().id(r1.getChangeId()).current().draftsAsList()).hasSize(1);
+    } finally {
+      cleanUpDrafts();
+    }
+  }
+
+  @Test
+  public void deleteDraftCommentsByQuery() throws Exception {
+    try {
+      PushOneCommit.Result r1 = createChange();
+      PushOneCommit.Result r2 = createChange();
+
+      createDraft(r1, PushOneCommit.FILE_NAME, "draft a");
+      createDraft(r2, PushOneCommit.FILE_NAME, "draft b");
+      assertThat(gApi.changes().id(r1.getChangeId()).current().draftsAsList()).hasSize(1);
+      assertThat(gApi.changes().id(r2.getChangeId()).current().draftsAsList()).hasSize(1);
+
+      List<DeletedDraftCommentInfo> result =
+          gApi.accounts()
+              .self()
+              .deleteDraftComments(new DeleteDraftCommentsInput("change:" + r1.getChangeId()));
+      assertThat(result).hasSize(1);
+      assertThat(result.get(0).change.changeId).isEqualTo(r1.getChangeId());
+      assertThat(result.get(0).deleted.stream().map(c -> c.message)).containsExactly("draft a");
+
+      assertThat(gApi.changes().id(r1.getChangeId()).current().draftsAsList()).isEmpty();
+      assertThat(gApi.changes().id(r2.getChangeId()).current().draftsAsList()).hasSize(1);
+    } finally {
+      cleanUpDrafts();
+    }
+  }
+
+  @Test
+  public void deleteOtherUsersDraftCommentsDisallowed() throws Exception {
+    try {
+      PushOneCommit.Result r = createChange();
+      setApiUser(user);
+      createDraft(r, PushOneCommit.FILE_NAME, "draft");
+      setApiUser(admin);
+      try {
+        gApi.accounts().id(user.id.get()).deleteDraftComments(new DeleteDraftCommentsInput());
+        assert_().fail("expected AuthException");
+      } catch (AuthException e) {
+        assertThat(e).hasMessageThat().isEqualTo("Cannot delete drafts of other user");
+      }
+    } finally {
+      cleanUpDrafts();
+    }
+  }
+
+  @Test
+  public void deleteDraftCommentsSkipsInvisibleChanges() throws Exception {
+    try {
+      createBranch(new Branch.NameKey(project, "secret"));
+      PushOneCommit.Result r1 = createChange();
+      PushOneCommit.Result r2 = createChange("refs/for/secret");
+
+      setApiUser(user);
+      createDraft(r1, PushOneCommit.FILE_NAME, "draft a");
+      createDraft(r2, PushOneCommit.FILE_NAME, "draft b");
+      assertThat(gApi.changes().id(r1.getChangeId()).current().draftsAsList()).hasSize(1);
+      assertThat(gApi.changes().id(r2.getChangeId()).current().draftsAsList()).hasSize(1);
+
+      block(project, "refs/heads/secret", Permission.READ, REGISTERED_USERS);
+      List<DeletedDraftCommentInfo> result =
+          gApi.accounts().self().deleteDraftComments(new DeleteDraftCommentsInput());
+      assertThat(result).hasSize(1);
+      assertThat(result.get(0).change.changeId).isEqualTo(r1.getChangeId());
+      assertThat(result.get(0).deleted.stream().map(c -> c.message)).containsExactly("draft a");
+
+      removePermission(project, "refs/heads/secret", Permission.READ);
+      assertThat(gApi.changes().id(r1.getChangeId()).current().draftsAsList()).isEmpty();
+      // Draft still exists since change wasn't visible when drafts where deleted.
+      assertThat(gApi.changes().id(r2.getChangeId()).current().draftsAsList()).hasSize(1);
+    } finally {
+      cleanUpDrafts();
+    }
+  }
+
+  private void createDraft(PushOneCommit.Result r, String path, String message) throws Exception {
+    DraftInput in = new DraftInput();
+    in.path = path;
+    in.line = 1;
+    in.message = message;
+    gApi.changes().id(r.getChangeId()).current().createDraft(in);
+  }
+
+  private void cleanUpDrafts() throws Exception {
+    for (TestAccount testAccount : accountCreator.getAll()) {
+      setApiUser(testAccount);
+      for (ChangeInfo changeInfo : gApi.changes().query("has:draft").get()) {
+        for (CommentInfo c :
+            gApi.changes()
+                .id(changeInfo.id)
+                .drafts()
+                .values()
+                .stream()
+                .flatMap(List::stream)
+                .collect(toImmutableList())) {
+          gApi.changes().id(changeInfo.id).revision(c.patchSet).draft(c.id).delete();
+        }
+      }
+    }
+  }
+
   private static Correspondence<GroupInfo, String> getGroupToNameCorrespondence() {
     return new Correspondence<GroupInfo, String>() {
       @Override
diff --git a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
index b3a5e2d..88803ec 100644
--- a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
@@ -1089,6 +1089,7 @@
 
       String ref = new Change.Id(id).toRefPrefix() + "1";
       eventRecorder.assertRefUpdatedEvents(projectName.get(), ref, null, commit, commit, null);
+      eventRecorder.assertChangeDeletedEvents(changeId, deleteAs.email);
     } finally {
       removePermission(project, "refs/*", Permission.DELETE_OWN_CHANGES);
       removePermission(project, "refs/*", Permission.DELETE_CHANGES);
diff --git a/javatests/com/google/gerrit/acceptance/rest/AccountsRestApiBindingsIT.java b/javatests/com/google/gerrit/acceptance/rest/AccountsRestApiBindingsIT.java
index 1a401b0..b0adba7 100644
--- a/javatests/com/google/gerrit/acceptance/rest/AccountsRestApiBindingsIT.java
+++ b/javatests/com/google/gerrit/acceptance/rest/AccountsRestApiBindingsIT.java
@@ -88,6 +88,7 @@
           RestCall.put("/accounts/%s/agreements"),
           RestCall.get("/accounts/%s/external.ids"),
           RestCall.post("/accounts/%s/external.ids:delete"),
+          RestCall.post("/accounts/%s/drafts:delete"),
           RestCall.get("/accounts/%s/oauthtoken"),
           RestCall.get("/accounts/%s/capabilities"),
           RestCall.get("/accounts/%s/capabilities/viewPlugins"),
diff --git a/plugins/hooks b/plugins/hooks
index cc74144..7185e5c 160000
--- a/plugins/hooks
+++ b/plugins/hooks
@@ -1 +1 @@
-Subproject commit cc74144db755a18c5a63764a336b93ab3d1be1fe
+Subproject commit 7185e5ce46646e952071befd9cf8f4267560b51d
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js b/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js
index 96a160e..60bf5ca 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-builder/gr-diff-builder.js
@@ -353,7 +353,7 @@
   };
 
   /**
-   * @param {number} line
+   * @param {GrDiffLine} line
    * @param {string=} opt_side
    * @return {!Object}
    */
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.js b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.js
index 3e9e796..6f61fb9 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host.js
@@ -28,6 +28,8 @@
     UNIFIED: 'UNIFIED_DIFF',
   };
 
+  const WHITESPACE_IGNORE_NONE = 'IGNORE_NONE';
+
   /**
    * @param {Object} diff
    * @return {boolean}
@@ -105,7 +107,10 @@
         type: Boolean,
         reflectToAttribute: true,
       },
-      noRenderOnPrefsChange: Boolean,
+      noRenderOnPrefsChange: {
+        type: Boolean,
+        value: false,
+      },
       comments: Object,
       lineWrapping: {
         type: Boolean,
@@ -167,12 +172,19 @@
         type: Object,
         value: null,
       },
+
+      _loadedWhitespaceLevel: String,
     },
 
     listeners: {
       'draft-interaction': '_handleDraftInteraction',
     },
 
+    observers: [
+      '_whitespaceChanged(prefs.ignore_whitespace, _loadedWhitespaceLevel,' +
+          ' noRenderOnPrefsChange)',
+    ],
+
     ready() {
       if (this._canReload()) {
         this.reload();
@@ -189,10 +201,15 @@
     reload() {
       this._loading = true;
       this._errorMessage = null;
+      const whitespaceLevel = this._getIgnoreWhitespace();
 
       const diffRequest = this._getDiff()
           .then(diff => {
+            this._loadedWhitespaceLevel = whitespaceLevel;
             this._reportDiff(diff);
+            if (this._getIgnoreWhitespace() !== WHITESPACE_IGNORE_NONE) {
+              return this._translateChunksToIgnore(diff);
+            }
             return diff;
           })
           .catch(e => {
@@ -321,6 +338,7 @@
             this.patchRange.basePatchNum,
             this.patchRange.patchNum,
             this.path,
+            this._getIgnoreWhitespace(),
             reject)
             .then(resolve);
       });
@@ -430,5 +448,63 @@
     _handleDraftInteraction() {
       this.$.reporting.recordDraftInteraction();
     },
+
+    /**
+     * Take a diff that was loaded with a ignore-whitespace other than
+     * IGNORE_NONE, and convert delta chunks labeled as common into shared
+     * chunks.
+     * @param {!Object} diff
+     * @returns {!Object}
+     */
+    _translateChunksToIgnore(diff) {
+      const newDiff = Object.assign({}, diff);
+      const mergedContent = [];
+
+      // Was the last chunk visited a shared chunk?
+      let lastWasShared = false;
+
+      for (const chunk of diff.content) {
+        if (lastWasShared && chunk.common && chunk.b) {
+          // The last chunk was shared and this chunk should be ignored, so
+          // add its revision content to the previous chunk.
+          mergedContent[mergedContent.length - 1].ab.push(...chunk.b);
+        } else if (chunk.common && !chunk.b) {
+          // If the chunk should be ignored, but it doesn't have revision
+          // content, then drop it and continue without updating lastWasShared.
+          continue;
+        } else if (lastWasShared && chunk.ab) {
+          // Both the last chunk and the current chunk are shared. Merge this
+          // chunk's shared content into the previous shared content.
+          mergedContent[mergedContent.length - 1].ab.push(...chunk.ab);
+        } else if (!lastWasShared && chunk.common && chunk.b) {
+          // If the previous chunk was not shared, but this one should be
+          // ignored, then add it as a shared chunk.
+          mergedContent.push({ab: chunk.b});
+        } else {
+          // Otherwise add the chunk as is.
+          mergedContent.push(chunk);
+        }
+
+        lastWasShared = !!mergedContent[mergedContent.length - 1].ab;
+      }
+
+      newDiff.content = mergedContent;
+      return newDiff;
+    },
+
+    _getIgnoreWhitespace() {
+      if (!this.prefs || !this.prefs.ignore_whitespace) {
+        return WHITESPACE_IGNORE_NONE;
+      }
+      return this.prefs.ignore_whitespace;
+    },
+
+    _whitespaceChanged(preferredWhitespaceLevel, loadedWhitespaceLevel,
+        noRenderOnPrefsChange) {
+      if (preferredWhitespaceLevel !== loadedWhitespaceLevel &&
+          !noRenderOnPrefsChange) {
+        this.reload();
+      }
+    },
   });
 })();
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.html b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.html
index a05d44f..f83253e 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff-host/gr-diff-host_test.html
@@ -775,5 +775,89 @@
         assert.isUndefined(reportStub.lastCall.args[1]);
       });
     });
+
+    suite('_translateChunksToIgnore', () => {
+      let content;
+
+      setup(() => {
+        content = [
+          {ab: ['one', 'two']},
+          {a: ['three'], b: ['different three']},
+          {b: ['four']},
+          {ab: ['five', 'six']},
+          {a: ['seven']},
+          {ab: ['eight', 'nine']},
+        ];
+      });
+
+      test('does nothing to unmarked diff', () => {
+        assert.deepEqual(element._translateChunksToIgnore({content}),
+            {content});
+      });
+
+      test('merges marked delta chunk', () => {
+        content[1].common = true;
+        assert.deepEqual(element._translateChunksToIgnore({content}), {
+          content: [
+            {ab: ['one', 'two', 'different three']},
+            {b: ['four']},
+            {ab: ['five', 'six']},
+            {a: ['seven']},
+            {ab: ['eight', 'nine']},
+          ],
+        });
+      });
+
+      test('merges marked addition chunk', () => {
+        content[2].common = true;
+        assert.deepEqual(element._translateChunksToIgnore({content}), {
+          content: [
+            {ab: ['one', 'two']},
+            {a: ['three'], b: ['different three']},
+            {ab: ['four', 'five', 'six']},
+            {a: ['seven']},
+            {ab: ['eight', 'nine']},
+          ],
+        });
+      });
+
+      test('merges multiple marked delta', () => {
+        content[1].common = true;
+        content[2].common = true;
+        assert.deepEqual(element._translateChunksToIgnore({content}), {
+          content: [
+            {ab: ['one', 'two', 'different three', 'four', 'five', 'six']},
+            {a: ['seven']},
+            {ab: ['eight', 'nine']},
+          ],
+        });
+      });
+
+      test('marked deletion chunks are omitted', () => {
+        content[4].common = true;
+        assert.deepEqual(element._translateChunksToIgnore({content}), {
+          content: [
+            {ab: ['one', 'two']},
+            {a: ['three'], b: ['different three']},
+            {b: ['four']},
+            {ab: ['five', 'six', 'eight', 'nine']},
+          ],
+        });
+      });
+
+      test('marked deltas can start shared chunks', () => {
+        content[0] = {a: ['one'], b: ['two'], common: true};
+        assert.deepEqual(element._translateChunksToIgnore({content}), {
+          content: [
+            {ab: ['two']},
+            {a: ['three'], b: ['different three']},
+            {b: ['four']},
+            {ab: ['five', 'six']},
+            {a: ['seven']},
+            {ab: ['eight', 'nine']},
+          ],
+        });
+      });
+    });
   });
 </script>
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-preferences/gr-diff-preferences.html b/polygerrit-ui/app/elements/diff/gr-diff-preferences/gr-diff-preferences.html
index 375e598..78814d4 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-preferences/gr-diff-preferences.html
+++ b/polygerrit-ui/app/elements/diff/gr-diff-preferences/gr-diff-preferences.html
@@ -60,7 +60,7 @@
         align-items: center;
         display: flex;
         padding: .35em 1.5em;
-        width: 20em;
+        width: 25em;
       }
       .pref:hover {
         background-color: var(--hover-background-color);
@@ -149,6 +149,15 @@
               type="checkbox"
               on-tap="_handleAutomaticReviewTap">
         </div>
+        <div class="pref">
+          <label for="ignoreWhitespace">Ignore Whitespace</label>
+          <select id="ignoreWhitespace" on-change="_handleIgnoreWhitespaceChange">
+            <option value="IGNORE_NONE">None</option>
+            <option value="IGNORE_TRAILING">Trailing</option>
+            <option value="IGNORE_LEADING_AND_TRAILING">Leading & trailing</option>
+            <option value="IGNORE_ALL">All</option>
+          </select>
+        </div>
       </div>
       <div class="actions">
         <gr-button id="cancelButton" link on-tap="_handleCancel">
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-preferences/gr-diff-preferences.js b/polygerrit-ui/app/elements/diff/gr-diff-preferences/gr-diff-preferences.js
index 47a3c2d..8fc90b9 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-preferences/gr-diff-preferences.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-preferences/gr-diff-preferences.js
@@ -67,6 +67,7 @@
       this.$.lineWrappingInput.checked = prefs.line_wrapping;
       this.$.syntaxHighlightInput.checked = prefs.syntax_highlighting;
       this.$.automaticReviewInput.checked = !prefs.manual_review;
+      this.$.ignoreWhitespace.value = prefs.ignore_whitespace;
     },
 
     _localPrefsChanged(changeRecord) {
@@ -79,6 +80,11 @@
       this.set('_newPrefs.context', parseInt(selectEl.value, 10));
     },
 
+    _handleIgnoreWhitespaceChange(e) {
+      const selectEl = Polymer.dom(e).rootTarget;
+      this.set('_newPrefs.ignore_whitespace', selectEl.value);
+    },
+
     _handleShowTabsTap(e) {
       this.set('_newPrefs.show_tabs', Polymer.dom(e).rootTarget.checked);
     },
diff --git a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff-line.js b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff-line.js
index 978058f..44bb52a 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff-line.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff-line.js
@@ -25,8 +25,10 @@
     this.highlights = [];
   }
 
+  /** @type {number|string} */
   GrDiffLine.prototype.afterNumber = 0;
 
+  /** @type {number|string} */
   GrDiffLine.prototype.beforeNumber = 0;
 
   GrDiffLine.prototype.contextGroup = null;
diff --git a/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view.html b/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view.html
index 18c1734..029ce88 100644
--- a/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view.html
+++ b/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view.html
@@ -348,6 +348,20 @@
                   on-change="_handleDiffSyntaxHighlightingChanged">
             </span>
           </section>
+          <section>
+          <div class="pref">
+            <span class="title">Ignore Whitespace</span>
+            <span class="value">
+              <gr-select bind-value="{{_diffPrefs.ignore_whitespace}}">
+                <select>
+                  <option value="IGNORE_NONE">None</option>
+                  <option value="IGNORE_TRAILING">Trailing</option>
+                  <option value="IGNORE_LEADING_AND_TRAILING">Leading & trailing</option>
+                  <option value="IGNORE_ALL">All</option>
+                </select>
+              </gr-select>
+            </span>
+          </div>
           <gr-button
               id="saveDiffPrefs"
               on-tap="_handleSaveDiffPreferences"
diff --git a/polygerrit-ui/app/elements/shared/gr-labeled-autocomplete/gr-labeled-autocomplete.html b/polygerrit-ui/app/elements/shared/gr-labeled-autocomplete/gr-labeled-autocomplete.html
new file mode 100644
index 0000000..5825301
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-labeled-autocomplete/gr-labeled-autocomplete.html
@@ -0,0 +1,72 @@
+<!--
+@license
+Copyright (C) 2018 The Android Open Source Project
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+<link rel="import" href="../../../bower_components/polymer/polymer.html">
+<link rel="import" href="../../shared/gr-autocomplete/gr-autocomplete.html">
+<link rel="import" href="../../../styles/shared-styles.html">
+
+<dom-module id="gr-labeled-autocomplete">
+  <template>
+    <style include="shared-styles">
+      :host {
+        display: block;
+        width: 12em;
+      }
+      #container {
+        background: var(--chip-background-color);
+        border-radius: 1em;
+        padding: .5em;
+      }
+      #header {
+        color: var(--deemphasized-text-color);
+        font-family: var(--font-family-bold);
+        font-size: var(--font-size-small);
+      }
+      #body {
+        display: flex;
+      }
+      gr-autocomplete {
+        height: 1.5em;
+        --gr-autocomplete: {
+          border: none;
+        }
+      }
+      #trigger {
+        border-left: 1px solid var(--deemphasized-text-color);
+        color: var(--deemphasized-text-color);
+        cursor: pointer;
+        padding-left: .4em;
+      }
+      #trigger:hover {
+        color: var(--primary-text-color);
+      }
+    </style>
+    <div id="container">
+      <div id="header">[[label]]</div>
+      <div id="body">
+        <gr-autocomplete
+            id="autocomplete"
+            threshold="[[_autocompleteThreshold]]"
+            query="[[query]]"
+            disabled="[[disabled]]"
+            placeholder="[[placeholder]]"
+            borderless></gr-autocomplete>
+        <div id="trigger" on-tap="_handleTriggerTap">▼</div>
+      </div>
+    </div>
+  </template>
+  <script src="gr-labeled-autocomplete.js"></script>
+</dom-module>
diff --git a/polygerrit-ui/app/elements/shared/gr-labeled-autocomplete/gr-labeled-autocomplete.js b/polygerrit-ui/app/elements/shared/gr-labeled-autocomplete/gr-labeled-autocomplete.js
new file mode 100644
index 0000000..cb3d546
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-labeled-autocomplete/gr-labeled-autocomplete.js
@@ -0,0 +1,73 @@
+/**
+ * @license
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+(function() {
+  'use strict';
+
+  Polymer({
+    is: 'gr-labeled-autocomplete',
+
+    /**
+     * Fired when a value is chosen.
+     *
+     * @event commit
+     */
+
+    properties: {
+
+      /**
+       * Used just like the query property of gr-autocomplete.
+       *
+       * @type {function(string): Promise<?>}
+       */
+      query: {
+        type: Function,
+        value() {
+          return function() {
+            return Promise.resolve([]);
+          };
+        },
+      },
+
+      text: {
+        type: String,
+        value: '',
+        notify: true,
+      },
+      label: String,
+      placeholder: String,
+      disabled: Boolean,
+
+      _autocompleteThreshold: {
+        type: Number,
+        value: 0,
+        readOnly: true,
+      },
+    },
+
+    _handleTriggerTap() {
+      this.$.autocomplete.focus();
+    },
+
+    setText(text) {
+      this.$.autocomplete.setText(text);
+    },
+
+    clear() {
+      this.setText('');
+    },
+  });
+})();
diff --git a/polygerrit-ui/app/elements/shared/gr-labeled-autocomplete/gr-labeled-autocomplete_test.html b/polygerrit-ui/app/elements/shared/gr-labeled-autocomplete/gr-labeled-autocomplete_test.html
new file mode 100644
index 0000000..f7632d3
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-labeled-autocomplete/gr-labeled-autocomplete_test.html
@@ -0,0 +1,58 @@
+<!DOCTYPE html>
+<!--
+@license
+Copyright (C) 2018 The Android Open Source Project
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+<meta name="viewport" content="width=device-width, minimum-scale=1.0, initial-scale=1.0, user-scalable=yes">
+<title>gr-labeled-autocomplete</title>
+
+<script src="../../../bower_components/webcomponentsjs/webcomponents-lite.min.js"></script>
+<script src="../../../bower_components/web-component-tester/browser.js"></script>
+<link rel="import" href="../../../test/common-test-setup.html"/>
+<link rel="import" href="gr-labeled-autocomplete.html">
+
+<script>void(0);</script>
+
+<test-fixture id="basic">
+  <template>
+    <gr-labeled-autocomplete></gr-labeled-autocomplete>
+  </template>
+</test-fixture>
+
+<script>
+  suite('gr-labeled-autocomplete tests', () => {
+    let element;
+    let sandbox;
+
+    setup(() => {
+      sandbox = sinon.sandbox.create();
+      element = fixture('basic');
+    });
+
+    teardown(() => { sandbox.restore(); });
+
+    test('tapping trigger focuses autocomplete', () => {
+      sandbox.stub(element.$.autocomplete, 'focus');
+      element._handleTriggerTap();
+      assert.isTrue(element.$.autocomplete.focus.calledOnce);
+    });
+
+    test('setText', () => {
+      sandbox.stub(element.$.autocomplete, 'setText');
+      element.setText('foo-bar');
+      assert.isTrue(element.$.autocomplete.setText.calledWith('foo-bar'));
+    });
+  });
+</script>
diff --git a/polygerrit-ui/app/elements/shared/gr-repo-branch-picker/gr-repo-branch-picker.html b/polygerrit-ui/app/elements/shared/gr-repo-branch-picker/gr-repo-branch-picker.html
new file mode 100644
index 0000000..d794dd6
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-repo-branch-picker/gr-repo-branch-picker.html
@@ -0,0 +1,60 @@
+<!--
+@license
+Copyright (C) 2018 The Android Open Source Project
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+<link rel="import" href="../../../bower_components/polymer/polymer.html">
+<link rel="import" href="../../../bower_components/iron-icon/iron-icon.html">
+<link rel="import" href="../../../styles/shared-styles.html">
+<link rel="import" href="../../../behaviors/gr-url-encoding-behavior/gr-url-encoding-behavior.html">
+<link rel="import" href="../../shared/gr-icons/gr-icons.html">
+<link rel="import" href="../../shared/gr-labeled-autocomplete/gr-labeled-autocomplete.html">
+<link rel="import" href="../../shared/gr-rest-api-interface/gr-rest-api-interface.html">
+
+<dom-module id="gr-repo-branch-picker">
+  <template>
+    <style include="shared-styles">
+      :host {
+        display: block;
+      }
+      gr-labeled-autocomplete,
+      iron-icon {
+        display: inline-block;
+      }
+      iron-icon {
+        margin-bottom: 1.2em;
+      }
+    </style>
+    <div>
+      <gr-labeled-autocomplete
+          id="repoInput"
+          label="Repository"
+          placeholder="Select repo"
+          on-commit="_repoCommitted"
+          query="[[_repoQuery]]">
+      </gr-labeled-autocomplete>
+      <iron-icon icon="gr-icons:chevron-right"></iron-icon>
+      <gr-labeled-autocomplete
+          id="branchInput"
+          label="Branch"
+          placeholder="Select branch"
+          disabled="[[_branchDisabled]]"
+          on-commit="_branchCommitted"
+          query="[[_query]]">
+      </gr-labeled-autocomplete>
+    </div>
+    <gr-rest-api-interface id="restAPI"></gr-rest-api-interface>
+  </template>
+  <script src="gr-repo-branch-picker.js"></script>
+</dom-module>
diff --git a/polygerrit-ui/app/elements/shared/gr-repo-branch-picker/gr-repo-branch-picker.js b/polygerrit-ui/app/elements/shared/gr-repo-branch-picker/gr-repo-branch-picker.js
new file mode 100644
index 0000000..e2298c3
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-repo-branch-picker/gr-repo-branch-picker.js
@@ -0,0 +1,109 @@
+/**
+ * @license
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+(function() {
+  'use strict';
+
+  const SUGGESTIONS_LIMIT = 15;
+  const REF_PREFIX = 'refs/heads/';
+
+  Polymer({
+    is: 'gr-repo-branch-picker',
+
+    properties: {
+      repo: {
+        type: String,
+        notify: true,
+        observer: '_repoChanged',
+      },
+      branch: {
+        type: String,
+        notify: true,
+      },
+      _branchDisabled: Boolean,
+      _query: {
+        type: Function,
+        value() {
+          return this._getRepoBranchesSuggestions.bind(this);
+        },
+      },
+      _repoQuery: {
+        type: Function,
+        value() {
+          return this._getRepoSuggestions.bind(this);
+        },
+      },
+    },
+
+    behaviors: [
+      Gerrit.URLEncodingBehavior,
+    ],
+
+    attached() {
+      if (this.repo) {
+        this.$.repoInput.setText(this.repo);
+      }
+    },
+
+    ready() {
+      this._branchDisabled = !this.repo;
+    },
+
+    _getRepoBranchesSuggestions(input) {
+      if (!this.repo) { return Promise.resolve([]); }
+      if (input.startsWith(REF_PREFIX)) {
+        input = input.substring(REF_PREFIX.length);
+      }
+      return this.$.restAPI.getRepoBranches(input, this.repo, SUGGESTIONS_LIMIT)
+          .then(this._branchResponseToSuggestions.bind(this));
+    },
+
+    _getRepoSuggestions(input) {
+      return this.$.restAPI.getRepos(input, SUGGESTIONS_LIMIT)
+          .then(this._repoResponseToSuggestions.bind(this));
+    },
+
+    _repoResponseToSuggestions(res) {
+      return res.map(repo => ({
+        name: repo.name,
+        value: this.singleDecodeURL(repo.id),
+      }));
+    },
+
+    _branchResponseToSuggestions(res) {
+      return Object.keys(res).map(key => {
+        let branch = res[key].ref;
+        if (branch.startsWith(REF_PREFIX)) {
+          branch = branch.substring(REF_PREFIX.length);
+        }
+        return {name: branch, value: branch};
+      });
+    },
+
+    _repoCommitted(e) {
+      this.repo = e.detail.value;
+    },
+
+    _branchCommitted(e) {
+      this.branch = e.detail.value;
+    },
+
+    _repoChanged() {
+      this.$.branchInput.clear();
+      this._branchDisabled = !this.repo;
+    },
+  });
+})();
diff --git a/polygerrit-ui/app/elements/shared/gr-repo-branch-picker/gr-repo-branch-picker_test.html b/polygerrit-ui/app/elements/shared/gr-repo-branch-picker/gr-repo-branch-picker_test.html
new file mode 100644
index 0000000..989e838
--- /dev/null
+++ b/polygerrit-ui/app/elements/shared/gr-repo-branch-picker/gr-repo-branch-picker_test.html
@@ -0,0 +1,140 @@
+<!DOCTYPE html>
+<!--
+@license
+Copyright (C) 2018 The Android Open Source Project
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+<meta name="viewport" content="width=device-width, minimum-scale=1.0, initial-scale=1.0, user-scalable=yes">
+<title>gr-repo-branch-picker</title>
+
+<script src="../../../bower_components/webcomponentsjs/webcomponents-lite.min.js"></script>
+<script src="../../../bower_components/web-component-tester/browser.js"></script>
+<link rel="import" href="../../../test/common-test-setup.html"/>
+<link rel="import" href="gr-repo-branch-picker.html">
+
+<script>void(0);</script>
+
+<test-fixture id="basic">
+  <template>
+    <gr-repo-branch-picker></gr-repo-branch-picker>
+  </template>
+</test-fixture>
+
+<script>
+  suite('gr-repo-branch-picker tests', () => {
+    let element;
+    let sandbox;
+
+    setup(() => {
+      sandbox = sinon.sandbox.create();
+      element = fixture('basic');
+    });
+
+    teardown(() => { sandbox.restore(); });
+
+    suite('_getRepoSuggestions', () => {
+      setup(() => {
+        sandbox.stub(element.$.restAPI, 'getRepos')
+            .returns(Promise.resolve([
+              {
+                id: 'plugins%2Favatars-external',
+                name: 'plugins/avatars-external',
+              }, {
+                id: 'plugins%2Favatars-gravatar',
+                name: 'plugins/avatars-gravatar',
+              }, {
+                id: 'plugins%2Favatars%2Fexternal',
+                name: 'plugins/avatars/external',
+              }, {
+                id: 'plugins%2Favatars%2Fgravatar',
+                name: 'plugins/avatars/gravatar',
+              },
+            ]));
+      });
+
+      test('converts to suggestion objects', () => {
+        const input = 'plugins/avatars';
+        return element._getRepoSuggestions(input).then(suggestions => {
+          assert.isTrue(element.$.restAPI.getRepos.calledWith(input));
+          const unencodedNames = [
+            'plugins/avatars-external',
+            'plugins/avatars-gravatar',
+            'plugins/avatars/external',
+            'plugins/avatars/gravatar',
+          ];
+          assert.deepEqual(suggestions.map(s => s.name), unencodedNames);
+          assert.deepEqual(suggestions.map(s => s.value), unencodedNames);
+        });
+      });
+    });
+
+    suite('_getRepoBranchesSuggestions', () => {
+      setup(() => {
+        sandbox.stub(element.$.restAPI, 'getRepoBranches')
+            .returns(Promise.resolve([
+              {ref: 'refs/heads/stable-2.10'},
+              {ref: 'refs/heads/stable-2.11'},
+              {ref: 'refs/heads/stable-2.12'},
+              {ref: 'refs/heads/stable-2.13'},
+              {ref: 'refs/heads/stable-2.14'},
+              {ref: 'refs/heads/stable-2.15'},
+            ]));
+      });
+
+      test('converts to suggestion objects', () => {
+        const repo = 'gerrit';
+        const branchInput = 'stable-2.1';
+        element.repo = repo;
+        return element._getRepoBranchesSuggestions(branchInput)
+            .then(suggestions => {
+              assert.isTrue(element.$.restAPI.getRepoBranches.calledWith(
+                  branchInput, repo, 15));
+              const refNames = [
+                'stable-2.10',
+                'stable-2.11',
+                'stable-2.12',
+                'stable-2.13',
+                'stable-2.14',
+                'stable-2.15',
+              ];
+              assert.deepEqual(suggestions.map(s => s.name), refNames);
+              assert.deepEqual(suggestions.map(s => s.value), refNames);
+            });
+      });
+
+      test('filters out ref prefix', () => {
+        const repo = 'gerrit';
+        const branchInput = 'refs/heads/stable-2.1';
+        element.repo = repo;
+        return element._getRepoBranchesSuggestions(branchInput)
+            .then(suggestions => {
+              assert.isTrue(element.$.restAPI.getRepoBranches.calledWith(
+                  'stable-2.1', repo, 15));
+            });
+      });
+
+      test('does not query when repo is unset', () => {
+        return element._getRepoBranchesSuggestions('')
+            .then(() => {
+              assert.isFalse(element.$.restAPI.getRepoBranches.called);
+              element.repo = 'gerrit';
+              return element._getRepoBranchesSuggestions('');
+            })
+            .then(() => {
+              assert.isTrue(element.$.restAPI.getRepoBranches.called);
+            });
+      });
+    });
+  });
+</script>
diff --git a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js
index af10b8371..c97c4c7 100644
--- a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js
+++ b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js
@@ -2134,13 +2134,16 @@
      *     index.
      * @param {number|string} patchNum
      * @param {string} path
+     * @param {string=} opt_whitespace the ignore-whitespace level for the diff
+     *     algorithm.
      * @param {function(?Response, string=)=} opt_errFn
      */
-    getDiff(changeNum, basePatchNum, patchNum, path, opt_errFn) {
+    getDiff(changeNum, basePatchNum, patchNum, path, opt_whitespace,
+        opt_errFn) {
       const params = {
         context: 'ALL',
         intraline: null,
-        whitespace: 'IGNORE_NONE',
+        whitespace: opt_whitespace || 'IGNORE_NONE',
       };
       if (this.isMergeParent(basePatchNum)) {
         params.parent = this.getParentIndex(basePatchNum);
diff --git a/polygerrit-ui/app/test/index.html b/polygerrit-ui/app/test/index.html
index d463d61..816700b 100644
--- a/polygerrit-ui/app/test/index.html
+++ b/polygerrit-ui/app/test/index.html
@@ -168,12 +168,14 @@
     'shared/gr-js-api-interface/gr-plugin-endpoints_test.html',
     'shared/gr-js-api-interface/gr-plugin-rest-api_test.html',
     'shared/gr-fixed-panel/gr-fixed-panel_test.html',
+    'shared/gr-labeled-autocomplete/gr-labeled-autocomplete_test.html',
     'shared/gr-lib-loader/gr-lib-loader_test.html',
     'shared/gr-limited-text/gr-limited-text_test.html',
     'shared/gr-linked-chip/gr-linked-chip_test.html',
     'shared/gr-linked-text/gr-linked-text_test.html',
     'shared/gr-list-view/gr-list-view_test.html',
     'shared/gr-page-nav/gr-page-nav_test.html',
+    'shared/gr-repo-branch-picker/gr-repo-branch-picker_test.html',
     'shared/gr-rest-api-interface/gr-auth_test.html',
     'shared/gr-rest-api-interface/gr-rest-api-interface_test.html',
     'shared/gr-rest-api-interface/gr-reviewer-updates-parser_test.html',