DevTools: cleanup button styles

third_party/WebKit/Source/devtools/front_end/help/ReleaseNoteView.js

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 Help.ReleaseNoteView = class extends UI.VBox {
   constructor() {
     super(true);
     this.registerRequiredCSS('help/releaseNote.css');
     var releaseNoteElement = this._createReleaseNoteElement(Help.latestReleaseNote());
     var topSection = this.contentElement.createChild('div', 'release-note-top-section');
@@ skipping 13 matching lines @@
       var listItem = contentContainer.createChild('li');
       var title = UI.createExternalLink(highlight.link, highlight.title + ' ', 'release-note-title');
       title.title = '';
       listItem.appendChild(title);
       var subtitle = UI.createExternalLink(highlight.link, highlight.subtitle + ' ', 'release-note-subtitle');
       subtitle.title = '';
       listItem.appendChild(subtitle);
     }
 
     var actionContainer = container.createChild('div', 'release-note-action-container');
-    var viewMoreButton = actionContainer.createChild('button');
-    viewMoreButton.textContent = Common.UIString('Learn more');
-    viewMoreButton.addEventListener('click', event => {
+    actionContainer.appendChild(UI.createTextButton(Common.UIString('Learn more'), event => {
       event.consume(true);
       InspectorFrontendHost.openInNewTab(releaseNote.link);
-    });
-
-    var closeButton = actionContainer.createChild('button', 'close-release-note');
-    closeButton.textContent = Common.UIString('Close');
-    closeButton.addEventListener('click', event => {
+    }));
+    actionContainer.appendChild(UI.createTextButton(Common.UIString('Close'), event => {
       event.consume(true);
       UI.inspectorView.closeDrawerTab(Help._releaseNoteViewId, true);
-    });
+    }, 'close-release-note'));
 
     var imageLink = UI.createExternalLink(releaseNote.link, ' ');
     imageLink.classList.add('release-note-image');
     imageLink.title = '';
     hbox.appendChild(imageLink);
     var image = imageLink.createChild('img');
     image.src = 'Images/whatsnew.png';
     return hbox;
   }
 };