Upgrade gr-editable-content with alert

Editable content now shows an alert when it reloads with content cached
in gr-storage.

Bug: Issue 6309
Change-Id: Id38b7eddf26e223a2899a0ffb1b3fa72398da0f0

polygerrit-ui/app/elements/shared/gr-editable-content/gr-editable-content.js

@@ -14,6 +14,7 @@
 (function() {
   'use strict';
 
+  const RESTORED_MESSAGE = 'Content restored from a previous edit.';
   const STORAGE_DEBOUNCE_INTERVAL_MS = 400;
 
   Polymer({
@@ -31,6 +32,12 @@
      * @event editable-content-cancel
      */
 
+    /**
+     * Fired when content is restored from storage.
+     *
+     * @event show-alert
+     */
+
     properties: {
       content: {
         notify: true,
@@ -81,10 +88,16 @@
 
       let content;
       if (this.storageKey) {
-        content = this.$.storage.getEditableContentItem(this.storageKey);
+        const storedContent =
+            this.$.storage.getEditableContentItem(this.storageKey);
+        if (storedContent && storedContent.message) {
+          content = storedContent.message;
+          this.dispatchEvent(new CustomEvent('show-alert',
+              {detail: {message: RESTORED_MESSAGE}, bubbles: true}));
+        }
       }
       if (!content) {
-        content = this.content;
+        content = this.content || '';
       }
 
       // TODO(wyatta) switch linkify sequence, see issue 5526.

polygerrit-ui/app/elements/shared/gr-editable-content/gr-editable-content_test.html

@@ -100,25 +100,30 @@ limitations under the License.
     });
 
     suite('storageKey and related behavior', () => {
+      let dispatchSpy;
       setup(() => {
         element.content = 'current content';
         element.storageKey = 'test';
+        dispatchSpy = sandbox.spy(element, 'dispatchEvent');
       });
 
       test('editing toggled to true, has stored data', () => {
         sandbox.stub(element.$.storage, 'getEditableContentItem')
-            .returns('stored content');
+            .returns({message: 'stored content'});
         element.editing = true;
 
         assert.equal(element._newContent, 'stored content');
+        assert.isTrue(dispatchSpy.called);
+        assert.equal(dispatchSpy.lastCall.args[0].type, 'show-alert');
       });
 
       test('editing toggled to true, has no stored data', () => {
         sandbox.stub(element.$.storage, 'getEditableContentItem')
-            .returns('');
+            .returns({});
         element.editing = true;
 
         assert.equal(element._newContent, 'current content');
+        assert.isFalse(dispatchSpy.called);
       });
 
       test('edits are cached', () => {