Reduce number of DOM Elements for Change Log

Gr-hovercard-account is shown only on hover. After fix, the app
creates all its DOM elements after hovering for the first time.
This saves 20 elements per account label, per 1 line in change log.

Gr-comment shows Save/Edit/Cancel actions only on drafts. After fix,
the app creates these actions only on drafts and not on all comments.
This saves 35 elements per comment.

Gr-message shows the Reply button only when expanded. After the fix
the app creates the button only after expanding for the first time.
This saves 20 elements per message.

When tested on /c/gerrit/+/251578 Change:
 - Show all entries was faster by 22% (1s -> 0.78s)
 - Expand all was faster by 47% (4.3s -> 2.3s)
 - Change pageload was faster by 3% (3.4s -> 3.3s)

Change-Id: Idfe2aebc78dda9555005aa5a33caeca31d583d8a

polygerrit-ui/app/elements/change/gr-message/gr-message_html.js

@@ -218,6 +218,7 @@ export const htmlTemplate = html`
             content="[[_messageContentExpanded]]"
             config="[[_projectConfig.commentlinks]]"
           ></gr-formatted-text>
+          <template is="dom-if" if="[[_expanded]]">
             <template is="dom-if" if="[[_messageContentExpanded]]">
               <div
                 class="replyActionContainer"
@@ -245,7 +246,6 @@ export const htmlTemplate = html`
                 </gr-button>
               </div>
             </template>
-          <template is="dom-if" if="[[_expanded]]">
             <template is="dom-if" if="[[!_isCleanerLogExperimentEnabled]]">
               <gr-comment-list
                 comments="[[comments]]"

polygerrit-ui/app/elements/change/gr-message/gr-message_test.html

@@ -62,7 +62,7 @@ suite('gr-message tests', () => {
         date: '2016-01-12 20:24:49.448000000',
         message: 'Uploaded patch set 1.',
         _revision_number: 1,
-        expanded: false,
+        expanded: true,
       };
 
       element.addEventListener('reply', e => {
@@ -87,7 +87,7 @@ suite('gr-message tests', () => {
         date: '2016-01-12 20:24:49.448000000',
         message: 'Uploaded patch set 1.',
         _revision_number: 1,
-        expanded: false,
+        expanded: true,
       };
 
       flushAsynchronousOperations();
@@ -105,7 +105,7 @@ suite('gr-message tests', () => {
         date: '2016-01-12 20:24:49.448000000',
         message: 'Uploaded patch set 1.',
         _revision_number: 1,
-        expanded: false,
+        expanded: true,
       };
 
       element.addEventListener('change-message-deleted', e => {
@@ -378,7 +378,7 @@ suite('gr-message tests', () => {
         date: '2016-01-12 20:24:49.448000000',
         message: 'Uploaded patch set 1.',
         _revision_number: 1,
-        expanded: false,
+        expanded: true,
       };
 
       flushAsynchronousOperations();
@@ -414,7 +414,7 @@ suite('gr-message tests', () => {
         date: '2016-01-12 20:24:49.448000000',
         message: 'Uploaded patch set 1.',
         _revision_number: 1,
-        expanded: false,
+        expanded: true,
       };
 
       flushAsynchronousOperations();
@@ -444,7 +444,7 @@ suite('gr-message tests', () => {
         date: '2016-01-12 20:24:49.448000000',
         message: 'not empty',
         _revision_number: 1,
-        expanded: false,
+        expanded: true,
       };
       flushAsynchronousOperations();
       replyEl = element.shadowRoot.querySelector('.replyActionContainer');

polygerrit-ui/app/elements/shared/gr-comment/gr-comment.js

@@ -483,7 +483,10 @@ class GrComment extends mixinBehaviors( [
 
     this.$.container.classList.toggle('editing', editing);
     if (this.comment && this.comment.id) {
-      this.shadowRoot.querySelector('.cancel').hidden = !editing;
+      const cancelButton = this.shadowRoot.querySelector('.cancel');
+      if (cancelButton) {
+        cancelButton.hidden = !editing;
+      }
     }
     if (this.comment) {
       this.comment.__editing = this.editing;

polygerrit-ui/app/elements/shared/gr-comment/gr-comment_html.js

@@ -361,6 +361,7 @@ export const htmlTemplate = html`
             Resolved
           </label>
         </div>
+        <template is="dom-if" if="[[draft]]">
           <div class="rightActions">
             <gr-button
               link=""
@@ -388,6 +389,7 @@ export const htmlTemplate = html`
               >Save</gr-button
             >
           </div>
+        </template>
       </div>
       <div class="robotActions" hidden$="[[!_showRobotActions]]">
         <template is="dom-if" if="[[isRobotComment]]">

polygerrit-ui/app/elements/shared/gr-comment/gr-comment_test.html

@@ -348,6 +348,8 @@ suite('gr-comment tests', () => {
     test('edit reports interaction', () => {
       const reportStub = sandbox.stub(element.reporting,
           'recordDraftInteraction');
+      element.draft = true;
+      flushAsynchronousOperations();
       MockInteractions.tap(element.shadowRoot
           .querySelector('.edit'));
       assert.isTrue(reportStub.calledOnce);
@@ -357,6 +359,7 @@ suite('gr-comment tests', () => {
       const reportStub = sandbox.stub(element.reporting,
           'recordDraftInteraction');
       element.draft = true;
+      flushAsynchronousOperations();
       MockInteractions.tap(element.shadowRoot
           .querySelector('.discard'));
       assert.isTrue(reportStub.calledOnce);
@@ -427,6 +430,7 @@ suite('gr-comment tests', () => {
           .querySelector('.robotActions').hasAttribute('hidden'));
 
       element.draft = true;
+      flushAsynchronousOperations();
       assert.isTrue(isVisible(element.shadowRoot
           .querySelector('.edit')), 'edit is visible');
       assert.isTrue(isVisible(element.shadowRoot
@@ -552,6 +556,8 @@ suite('gr-comment tests', () => {
 
       // When the edit button is pressed, should still see the actions
       // and also textarea
+      element.draft = true;
+      flushAsynchronousOperations();
       MockInteractions.tap(element.shadowRoot
           .querySelector('.edit'));
       flushAsynchronousOperations();
@@ -655,6 +661,8 @@ suite('gr-comment tests', () => {
 
     test('draft creation/cancellation', done => {
       assert.isFalse(element.editing);
+      element.draft = true;
+      flushAsynchronousOperations();
       MockInteractions.tap(element.shadowRoot
           .querySelector('.edit'));
       assert.isTrue(element.editing);
@@ -787,6 +795,7 @@ suite('gr-comment tests', () => {
       const cancelDebounce = sandbox.stub(element, 'cancelDebouncer');
 
       element.draft = true;
+      flushAsynchronousOperations();
       MockInteractions.tap(element.shadowRoot
           .querySelector('.edit'));
       element._messageText = 'good news, everyone!';
@@ -852,6 +861,7 @@ suite('gr-comment tests', () => {
       const saveStub = sandbox.stub(element, 'save').returns(Promise.resolve());
       element.showActions = true;
       element.draft = true;
+      flushAsynchronousOperations();
       MockInteractions.tap(element.$.header);
       MockInteractions.tap(element.shadowRoot
           .querySelector('.edit'));

polygerrit-ui/app/elements/shared/gr-hovercard-account/gr-hovercard-account_html.js

@@ -64,6 +64,7 @@ export const htmlTemplate = html`
     }
   </style>
   <div id="container" role="tooltip" tabindex="-1">
+    <template is="dom-if" if="[[_isShowing]]">
       <div class="top">
         <div class="avatar">
           <gr-avatar account="[[account]]" image-size="56"></gr-avatar>
@@ -92,5 +93,6 @@ export const htmlTemplate = html`
         <iron-icon icon="gr-icons:attention"></iron-icon>
         <span>It is this user's turn to take action.</span>
       </div>
+    </template>
   </div>
 `;

polygerrit-ui/app/elements/shared/gr-hovercard-account/gr-hovercard-account_test.html

@@ -49,6 +49,8 @@ limitations under the License.
     setup(() => {
       element = fixture('basic');
       element.account = Object.assign({}, ACCOUNT);
+      element.show({});
+      flushAsynchronousOperations();
     });
 
     test('account name is shown', () => {