Do not repeatedly add the 'revert' message modifications

As part of the fix for
https://bugs.chromium.org/p/chromium/issues/detail?id=624383 an API
event callback was added that allowed plugins to modify the revert
message in the revert dialog.
The problem is that the modified revert message persisted even when the
dialog was cancelled. This caused the same block to be repeated added to
the revert dialog.

This change ensures that the revert message is constructed right before
the dialog is shown. All modifications via the API event callback are
now discarded if the dialog is cancelled.

BUG= https://bugs.chromium.org/p/chromium/issues/detail?id=637300

Change-Id: Iac2725f6872913e9edf9022df928a36d4b6ad6e6

polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions.js

@@ -274,6 +274,7 @@
       if (type === ActionType.REVISION) {
         this._handleRevisionAction(key);
       } else if (key === ChangeActions.REVERT) {
+        this.$.confirmRevertDialog.populateRevertMessage();
         this.$.confirmRevertDialog.message = this._modifyRevertMsg();
         this._showActionDialog(this.$.confirmRevertDialog);
       } else if (key === ChangeActions.ABANDON) {

polygerrit-ui/app/elements/change/gr-change-actions/gr-change-actions_test.html

@@ -244,18 +244,25 @@ limitations under the License.
         var newRevertMsg = 'Modified revert msg';
         var modifyRevertMsgStub = sinon.stub(element, '_modifyRevertMsg',
             function() { return newRevertMsg; });
+        var populateRevertMsgStub = sinon.stub(
+            element.$.confirmRevertDialog, 'populateRevertMessage',
+            function() { return 'original msg'; });
         flush(function() {
           var revertButton = element.$$('gr-button[data-action-key="revert"]');
           MockInteractions.tap(revertButton);
 
           assert.equal(element.$.confirmRevertDialog.message, newRevertMsg);
 
+          populateRevertMsgStub.restore();
           modifyRevertMsgStub.restore();
           done();
         });
       });
 
       test('works', function() {
+        var populateRevertMsgStub = sinon.stub(
+            element.$.confirmRevertDialog, 'populateRevertMessage',
+            function() { return 'original msg'; });
         var revertButton = element.$$('gr-button[data-action-key="revert"]');
         MockInteractions.tap(revertButton);
 
@@ -276,6 +283,7 @@ limitations under the License.
           '/revert', action, false, {
             message: 'foo message',
           }]);
+        populateRevertMsgStub.restore();
       });
     });
   });

polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog.js

@@ -32,15 +32,12 @@
     properties: {
       branch: String,
       message: String,
-      commitInfo: {
-        type: Object,
-        observer: '_commitInfoChanged',
-      },
+      commitInfo: Object,
     },
 
-    _commitInfoChanged: function(commitInfo) {
+    populateRevertMessage: function() {
       // Figure out what the revert title should be.
-      var originalTitle = commitInfo.message.split('\n')[0];
+      var originalTitle = this.commitInfo.message.split('\n')[0];
       var revertTitle = 'Revert of ' + originalTitle;
       if (originalTitle.startsWith('Revert of ')) {
         revertTitle = 'Reland of ' +
@@ -50,7 +47,7 @@
                       originalTitle.substring('Reland of '.length);
       }
       // Add '> ' in front of the original commit text.
-      var originalCommitText = commitInfo.message.replace(/^/gm, '> ');
+      var originalCommitText = this.commitInfo.message.replace(/^/gm, '> ');
 
       this.message = revertTitle + '\n\n' +
                      'Reason for revert: <INSERT REASONING HERE>\n\n' +

polygerrit-ui/app/elements/change/gr-confirm-revert-dialog/gr-confirm-revert-dialog_test.html

@@ -39,9 +39,10 @@ limitations under the License.
     });
 
     test('single line', function() {
-      assert(element.message == null);
-      element.commitInfo = { message: 'one line commit' };
-      console.log(element.message);
+      assert.isNotOk(element.message);
+      element.commitInfo = {message: 'one line commit'};
+      assert.isNotOk(element.message);
+      element.populateRevertMessage();
       var expected = 'Revert of one line commit\n\n' +
                      'Reason for revert: <INSERT REASONING HERE>\n\n' +
                      'Original issue\'s description:\n' +
@@ -50,9 +51,10 @@ limitations under the License.
     });
 
     test('multi line', function() {
-      assert(element.message == null);
-      element.commitInfo = { message: 'many lines\ncommit\n\nmessage\n' };
-      console.log(element.message);
+      assert.isNotOk(element.message);
+      element.commitInfo = {message: 'many lines\ncommit\n\nmessage\n'};
+      assert.isNotOk(element.message);
+      element.populateRevertMessage();
       var expected = 'Revert of many lines\n\n' +
                      'Reason for revert: <INSERT REASONING HERE>\n\n' +
                      'Original issue\'s description:\n' +