Remove alert-based error reporting

Migrates all alert calls to toasts. Also corrects one test that checked
for an alert on the window.

Bug: Issue 6701
Change-Id: I4d41790f63edc15873014df4f98013ac2bb2af7c

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

@@ -14,6 +14,9 @@
 (function() {
   'use strict';
 
+  const ERR_BRANCH_EMPTY = 'The destination branch can’t be empty.';
+  const ERR_COMMIT_EMPTY = 'The commit message can’t be empty.';
+  const ERR_REVISION_ACTIONS = 'Couldn’t load revision actions.';
   /**
    * @enum {number}
    */
@@ -293,8 +296,7 @@
         this.revisionActions = revisionActions;
         this._loading = false;
       }).catch(err => {
-        alert('Couldn’t load revision actions. Check the console ' +
-            'and contact the PolyGerrit team for assistance.');
+        this.fire('show-alert', {message: ERR_REVISION_ACTIONS});
         this._loading = false;
         throw err;
       });
@@ -696,11 +698,11 @@
       const el = this.$.confirmCherrypick;
       if (!el.branch) {
         // TODO(davido): Fix error handling
-        alert('The destination branch can’t be empty.');
+        this.fire('show-alert', {message: ERR_BRANCH_EMPTY});
         return;
       }
       if (!el.message) {
-        alert('The commit message can’t be empty.');
+        this.fire('show-alert', {message: ERR_COMMIT_EMPTY});
         return;
       }
       this.$.overlay.close();

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

@@ -14,6 +14,9 @@
 (function() {
   'use strict';
 
+  const ERR_COMMIT_NOT_FOUND =
+      'Unable to find the commit hash of this change.';
+
   Polymer({
     is: 'gr-confirm-revert-dialog',
 
@@ -38,7 +41,7 @@
       const originalTitle = message.split('\n')[0];
       const revertTitle = `Revert "${originalTitle}"`;
       if (!commitHash) {
-        alert('Unable to find the commit hash of this change.');
+        this.fire('show-alert', {message: ERR_COMMIT_NOT_FOUND});
         return;
       }
       const revertCommitText = `This reverts commit ${commitHash}.`;

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

@@ -34,17 +34,21 @@ limitations under the License.
 <script>
   suite('gr-confirm-revert-dialog tests', () => {
     let element;
+    let sandbox;
 
     setup(() => {
       element = fixture('basic');
+      sandbox =sinon.sandbox.create();
     });
 
+    teardown(() => sandbox.restore());
+
     test('no match', () => {
       assert.isNotOk(element.message);
-      const alertStub = sinon.stub(window, 'alert');
+      const alertStub = sandbox.stub();
+      element.addEventListener('show-alert', alertStub);
       element.populateRevertMessage('not a commitHash in sight', undefined);
       assert.isTrue(alertStub.calledOnce);
-      alertStub.restore();
     });
 
     test('single line', () => {

polygerrit-ui/app/elements/diff/gr-diff-view/gr-diff-view.js

@@ -17,6 +17,8 @@
   const COMMIT_MESSAGE_PATH = '/COMMIT_MSG';
   const MERGE_LIST_PATH = '/MERGE_LIST';
 
+  const ERR_REVIEW_STATUS = 'Couldn’t change file review status.';
+
   const COMMENT_SAVE = 'Try again when all comments have saved.';
 
   const DiffSides = {
@@ -191,8 +193,7 @@
     _setReviewed(reviewed) {
       this.$.reviewed.checked = reviewed;
       this._saveReviewedState(reviewed).catch(err => {
-        alert('Couldn’t change file review status. Check the console ' +
-            'and contact the PolyGerrit team for assistance.');
+        this.fire('show-alert', {message: ERR_REVIEW_STATUS});
         throw err;
       });
     },