[DevTools] Do not inherit ObjectPopoverHelper from PopoverHelper.

third_party/WebKit/Source/devtools/front_end/animation/AnimationTimeline.js

 // Copyright (c) 2015 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.
 /**
  * @implements {SDK.SDKModelObserver<!Animation.AnimationModel>}
  * @unrestricted
  */
 Animation.AnimationTimeline = class extends UI.VBox {
   constructor() {
     super(true);
@@ skipping 154 matching lines @@
    * @param {!Element} element
    * @param {!Event} event
    * @return {!Element|!AnchorBox|undefined}
    */
   _getPopoverAnchor(element, event) {
     if (element.isDescendant(this._previewContainer))
       return element;
   }
 
   /**
-   * @param {!Element} anchor
+   * @param {!Element|!AnchorBox} anchor
    * @param {!UI.GlassPane} popover
    * @return {!Promise<boolean>}
    */
   _showPopover(anchor, popover) {
     var animGroup;
     for (var group of this._previewMap.keysArray()) {
       if (this._previewMap.get(group).element === anchor.parentElement)
         animGroup = group;
     }
     console.assert(animGroup);
@@ skipping 547 matching lines @@
   static parse(text) {
     var match = text.match(/^steps\((\d+), (start|middle)\)$/);
     if (match)
       return new Animation.AnimationTimeline.StepTimingFunction(parseInt(match[1], 10), match[2]);
     match = text.match(/^steps\((\d+)\)$/);
     if (match)
       return new Animation.AnimationTimeline.StepTimingFunction(parseInt(match[1], 10), 'end');
     return null;
   }
 };