diff --git a/java/com/google/gerrit/json/EnumTypeAdapterFactory.java b/java/com/google/gerrit/json/EnumTypeAdapterFactory.java
index dc74f67..21c4891 100644
--- a/java/com/google/gerrit/json/EnumTypeAdapterFactory.java
+++ b/java/com/google/gerrit/json/EnumTypeAdapterFactory.java
@@ -34,7 +34,7 @@
 public class EnumTypeAdapterFactory implements TypeAdapterFactory {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
 
-  @SuppressWarnings({"unchecked"})
+  @SuppressWarnings({"rawtypes", "unchecked"})
   @Override
   public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
     TypeAdapter<T> defaultEnumAdapter = TypeAdapters.ENUM_FACTORY.create(gson, typeToken);
@@ -43,7 +43,7 @@
       return null;
     }
 
-    return (TypeAdapter<T>) new EnumTypeAdapter(defaultEnumAdapter, typeToken);
+    return new EnumTypeAdapter(defaultEnumAdapter, typeToken);
   }
 
   private static class EnumTypeAdapter<T extends Enum<T>> extends TypeAdapter<T> {
diff --git a/javatests/com/google/gerrit/json/JsonEnumMappingTest.java b/javatests/com/google/gerrit/json/JsonEnumMappingTest.java
index 6e57b01..dd710f9 100644
--- a/javatests/com/google/gerrit/json/JsonEnumMappingTest.java
+++ b/javatests/com/google/gerrit/json/JsonEnumMappingTest.java
@@ -71,10 +71,6 @@
 
   private static class TestData {
     TestEnum value;
-
-    public TestData(TestEnum value) {
-      this.value = value;
-    }
   }
 
   private enum TestEnum {
diff --git a/polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list.js b/polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list.js
index 077af1f..8500e3b 100644
--- a/polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list.js
+++ b/polygerrit-ui/app/elements/change-list/gr-change-list/gr-change-list.js
@@ -159,6 +159,11 @@
     },
 
     _computePreferences(account, preferences) {
+      // Polymer 2: check for undefined
+      if ([account, preferences].some(arg => arg === undefined)) {
+        return;
+      }
+
       this.changeTableColumns = this.columnNames;
 
       if (account) {
diff --git a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js
index 90641df..54e2edd 100644
--- a/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js
+++ b/polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js
@@ -590,6 +590,15 @@
 
     _actionsChanged(actionsChangeRecord, revisionActionsChangeRecord,
         additionalActionsChangeRecord) {
+      // Polymer 2: check for undefined
+      if ([
+        actionsChangeRecord,
+        revisionActionsChangeRecord,
+        additionalActionsChangeRecord,
+      ].some(arg => arg === undefined)) {
+        return;
+      }
+
       const additionalActions = (additionalActionsChangeRecord &&
           additionalActionsChangeRecord.base) || [];
       this.hidden = this._keyCount(actionsChangeRecord) === 0 &&
@@ -620,6 +629,15 @@
 
     _editStatusChanged(editMode, editPatchsetLoaded,
         editBasedOnCurrentPatchSet, disableEdit) {
+      // Polymer 2: check for undefined
+      if ([
+        editMode,
+        editBasedOnCurrentPatchSet,
+        disableEdit,
+      ].some(arg => arg === undefined)) {
+        return;
+      }
+
       if (disableEdit) {
         this._deleteAndNotify('publishEdit');
         this._deleteAndNotify('rebaseEdit');
@@ -1344,6 +1362,17 @@
      */
     _computeAllActions(changeActionsRecord, revisionActionsRecord,
         primariesRecord, additionalActionsRecord, change) {
+      // Polymer 2: check for undefined
+      if ([
+        changeActionsRecord,
+        revisionActionsRecord,
+        primariesRecord,
+        additionalActionsRecord,
+        change,
+      ].some(arg => arg === undefined)) {
+        return [];
+      }
+
       const revisionActionValues = this._getActionValues(revisionActionsRecord,
           primariesRecord, additionalActionsRecord, ActionType.REVISION);
       const changeActionValues = this._getActionValues(changeActionsRecord,
diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js
index 66667ba..841e3d8 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view.js
@@ -795,7 +795,12 @@
       });
     },
 
-    _paramsAndChangeChanged(value) {
+    _paramsAndChangeChanged(value, change) {
+      // Polymer 2: check for undefined
+      if ([value, change].some(arg => arg === undefined)) {
+        return;
+      }
+
       // If the change number or patch range is different, then reset the
       // selected file index.
       const patchRangeState = this.viewState.patchRange;
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.js
index f4523cf..2f098de 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-cherrypick-dialog/gr-confirm-cherrypick-dialog.js
@@ -60,6 +60,15 @@
     ],
 
     _computeMessage(changeStatus, commitNum, commitMessage) {
+      // Polymer 2: check for undefined
+      if ([
+        changeStatus,
+        commitNum,
+        commitMessage,
+      ].some(arg => arg === undefined)) {
+        return;
+      }
+
       let newMessage = commitMessage;
 
       if (changeStatus === 'MERGED') {
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.js b/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.js
index 1c3bcfb..22ce27e 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-confirm-rebase-dialog/gr-confirm-rebase-dialog.js
@@ -144,6 +144,11 @@
      * the corresponding value to be submitted.
      */
     _updateSelectedOption(rebaseOnCurrent, hasParent) {
+      // Polymer 2: check for undefined
+      if ([rebaseOnCurrent, hasParent].some(arg => arg === undefined)) {
+        return;
+      }
+
       if (this._displayParentOption(rebaseOnCurrent, hasParent)) {
         this.$.rebaseOnParentInput.checked = true;
       } else if (this._displayTipOption(rebaseOnCurrent, hasParent)) {
diff --git a/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.js b/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.js
index a802fb9..aff1e0a 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.js
+++ b/polygerrit-ui/app/elements/change/gr-file-list-header/gr-file-list-header.js
@@ -137,6 +137,11 @@
     },
 
     _computePatchSetDescription(change, patchNum) {
+      // Polymer 2: check for undefined
+      if ([change, patchNum].some(arg => arg === undefined)) {
+        return;
+      }
+
       const rev = this.getRevisionByPatchNum(change.revisions, patchNum);
       this._patchsetDescription = (rev && rev.description) ?
           rev.description.substring(0, PATCH_DESC_MAX_LENGTH) : '';
diff --git a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js
index 4f160e4..1620610 100644
--- a/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js
+++ b/polygerrit-ui/app/elements/change/gr-file-list/gr-file-list.js
@@ -817,6 +817,17 @@
     },
 
     _computeFiles(filesByPath, changeComments, patchRange, reviewed, loading) {
+      // Polymer 2: check for undefined
+      if ([
+        filesByPath,
+        changeComments,
+        patchRange,
+        reviewed,
+        loading,
+      ].some(arg => arg === undefined)) {
+        return;
+      }
+
       // Await all promises resolving from reload. @See Issue 9057
       if (loading || !changeComments) { return; }
 
@@ -904,6 +915,11 @@
     },
 
     _computePatchSetDescription(revisions, patchNum) {
+      // Polymer 2: check for undefined
+      if ([revisions, patchNum].some(arg => arg === undefined)) {
+        return '';
+      }
+
       const rev = this.getRevisionByPatchNum(revisions, patchNum);
       return (rev && rev.description) ?
           rev.description.substring(0, PATCH_DESC_MAX_LENGTH) : '';
diff --git a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js
index eeec437..4166511 100644
--- a/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js
+++ b/polygerrit-ui/app/elements/change/gr-related-changes-list/gr-related-changes-list.js
@@ -292,6 +292,17 @@
 
     _resultsChanged(related, submittedTogether, conflicts,
         cherryPicks, sameTopic) {
+      // Polymer 2: check for undefined
+      if ([
+        related,
+        submittedTogether,
+        conflicts,
+        cherryPicks,
+        sameTopic,
+      ].some(arg => arg === undefined)) {
+        return;
+      }
+
       const results = [
         related && related.changes,
         submittedTogether && submittedTogether.changes,
diff --git a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
index cd42606..640cbc8 100644
--- a/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
+++ b/polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.js
@@ -623,6 +623,11 @@
     },
 
     _changeUpdated(changeRecord, owner) {
+      // Polymer 2: check for undefined
+      if ([changeRecord, owner].some(arg => arg === undefined)) {
+        return;
+      }
+
       this._rebuildReviewerArrays(changeRecord.base, owner);
     },
 
diff --git a/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.js b/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.js
index 43ea7f0..63e0647 100644
--- a/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.js
+++ b/polygerrit-ui/app/elements/change/gr-reviewer-list/gr-reviewer-list.js
@@ -165,6 +165,11 @@
     },
 
     _reviewersChanged(changeRecord, owner) {
+      // Polymer 2: check for undefined
+      if ([changeRecord, owner].some(arg => arg === undefined)) {
+        return;
+      }
+
       let result = [];
       const reviewers = changeRecord.base;
       for (const key in reviewers) {
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 2c14609..bce3d07 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
@@ -742,6 +742,15 @@
     _whitespaceChanged(
         preferredWhitespaceLevel, loadedWhitespaceLevel,
         noRenderOnPrefsChange) {
+      // Polymer 2: check for undefined
+      if ([
+        preferredWhitespaceLevel,
+        loadedWhitespaceLevel,
+        noRenderOnPrefsChange,
+      ].some(arg => arg === undefined)) {
+        return;
+      }
+
       if (preferredWhitespaceLevel !== loadedWhitespaceLevel &&
           !noRenderOnPrefsChange) {
         this.reload();
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.js b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.js
index d604df2..0c1facd 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.js
@@ -260,6 +260,11 @@
     },
 
     _getFiles(changeNum, patchRangeRecord) {
+      // Polymer 2: check for undefined
+      if ([changeNum, patchRangeRecord].some(arg => arg === undefined)) {
+        return;
+      }
+
       const patchRange = patchRangeRecord.base;
       return this.$.restAPI.getChangeFilePathsAsSpeciallySortedArray(
           changeNum, patchRange).then(files => {
@@ -680,6 +685,11 @@
     },
 
     _setReviewedObserver(_loggedIn, paramsRecord, _prefs) {
+      // Polymer 2: check for undefined
+      if ([_loggedIn, paramsRecord, _prefs].some(arg => arg === undefined)) {
+        return;
+      }
+
       const params = paramsRecord.base || {};
       if (!_loggedIn) { return; }
 
diff --git a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.js b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.js
index 1bafe48..c69b313 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.js
+++ b/polygerrit-ui/app/elements/diff/gr-diff/gr-diff.js
@@ -297,6 +297,11 @@
     },
 
     _enableSelectionObserver(loggedIn, isAttached) {
+      // Polymer 2: check for undefined
+      if ([loggedIn, isAttached].some(arg => arg === undefined)) {
+        return;
+      }
+
       if (loggedIn && isAttached) {
         this.listen(document, 'selectionchange', '_handleSelectionChange');
         this.listen(document, 'mouseup', '_handleMouseUp');
diff --git a/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.js b/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.js
index c36ec21..34f1ff9 100644
--- a/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.js
+++ b/polygerrit-ui/app/elements/shared/gr-autocomplete/gr-autocomplete.js
@@ -242,8 +242,13 @@
     },
 
     _updateSuggestions(text, threshold, noDebounce) {
+      // Polymer 2: check for undefined
+      if ([text, threshold, noDebounce].some(arg => arg === undefined)) {
+        return;
+      }
+
       if (this._disableSuggestions) { return; }
-      if (text === undefined || text.length < threshold) {
+      if (text.length < threshold) {
         this._suggestions = [];
         this.value = '';
         return;
diff --git a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.js b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.js
index 57835a3..cf2f57d 100644
--- a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.js
+++ b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.js
@@ -211,6 +211,11 @@
     },
 
     _calculateActionstoShow(showActions, isRobotComment) {
+      // Polymer 2: check for undefined
+      if ([showActions, isRobotComment].some(arg => arg === undefined)) {
+        return;
+      }
+
       this._showHumanActions = showActions && !isRobotComment;
       this._showRobotActions = showActions && isRobotComment;
     },
@@ -601,6 +606,11 @@
     },
 
     _loadLocalDraft(changeNum, patchNum, comment) {
+      // Polymer 2: check for undefined
+      if ([changeNum, patchNum, comment].some(arg => arg === undefined)) {
+        return;
+      }
+
       // Only apply local drafts to comments that haven't been saved
       // remotely, and haven't been given a default message already.
       //
diff --git a/polygerrit-ui/app/elements/shared/gr-dropdown-list/gr-dropdown-list.js b/polygerrit-ui/app/elements/shared/gr-dropdown-list/gr-dropdown-list.js
index bcf3729..b6d909d 100644
--- a/polygerrit-ui/app/elements/shared/gr-dropdown-list/gr-dropdown-list.js
+++ b/polygerrit-ui/app/elements/shared/gr-dropdown-list/gr-dropdown-list.js
@@ -104,6 +104,11 @@
     },
 
     _handleValueChange(value, items) {
+      // Polymer 2: check for undefined
+      if ([value, items].some(arg => arg === undefined)) {
+        return;
+      }
+
       if (!value) { return; }
       const selectedObj = items.find(item => {
         return item.value + '' === value + '';
diff --git a/polygerrit-ui/app/elements/shared/gr-limited-text/gr-limited-text.js b/polygerrit-ui/app/elements/shared/gr-limited-text/gr-limited-text.js
index 44a8791..479dd1e 100644
--- a/polygerrit-ui/app/elements/shared/gr-limited-text/gr-limited-text.js
+++ b/polygerrit-ui/app/elements/shared/gr-limited-text/gr-limited-text.js
@@ -66,6 +66,11 @@
      * enabled.
      */
     _updateTitle(text, limit, tooltipLimit) {
+      // Polymer 2: check for undefined
+      if ([text, limit, tooltipLimit].some(arg => arg === undefined)) {
+        return;
+      }
+
       this.hasTooltip = !!limit && !!text && text.length > limit;
       if (this.hasTooltip) {
         this.setAttribute('title', text.substr(0, tooltipLimit));