Add confirm-revert-change endpoint

Bug: Issue 11233
Change-Id: I98f0574d532b319d05c9210b94811be6c292ab3e
diff --git a/Documentation/pg-plugin-endpoints.txt b/Documentation/pg-plugin-endpoints.txt
index ff62da1..10db5ba 100644
--- a/Documentation/pg-plugin-endpoints.txt
+++ b/Documentation/pg-plugin-endpoints.txt
@@ -130,6 +130,11 @@
 === header-title
 This endpoint wraps the title-text in the application header.
 
+=== confirm-revert-change
+This endpoint is inside the confirm revert dialog. By default it displays a
+generic confirmation message regarding reverting the change. Plugins may add
+content to this message or replace it entirely.
+
 === confirm-submit-change
 This endpoint is inside the confirm submit dialog. By default it displays a
 generic confirmation message regarding submission of the change. Plugins may add
diff --git a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.html b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.html
index e7dd6ac..5e10870 100644
--- a/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.html
+++ b/polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.html
@@ -54,15 +54,17 @@
         on-cancel="_handleCancelTap">
       <div class="header" slot="header">Revert Merged Change</div>
       <div class="main" slot="main">
-        <label for="messageInput">
-          Revert Commit Message
-        </label>
-        <iron-autogrow-textarea
-            id="messageInput"
-            class="message"
-            autocomplete="on"
-            max-rows="15"
-            bind-value="{{message}}"></iron-autogrow-textarea>
+        <gr-endpoint-decorator name="confirm-revert-change">
+          <label for="messageInput">
+            Revert Commit Message
+          </label>
+          <iron-autogrow-textarea
+              id="messageInput"
+              class="message"
+              autocomplete="on"
+              max-rows="15"
+              bind-value="{{message}}"></iron-autogrow-textarea>
+        </gr-endpoint-decorator>
       </div>
     </gr-dialog>
   </template>