DevTools: migrate StylesSidebarPane to shadow

third_party/WebKit/Source/devtools/front_end/elements/ElementsSidebarPane.js

 // Copyright (c) 2014 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.
 /**
  * @unrestricted
  */
 Elements.ElementsSidebarPane = class extends UI.VBox {
-  /**
-   * @param {boolean=} isWebComponent
-   */
-  constructor(isWebComponent) {
-    super(isWebComponent);
+  constructor() {
+    super(true);
     this.element.classList.add('flex-none');
     this._computedStyleModel = new Elements.ComputedStyleModel();
     this._computedStyleModel.addEventListener(
         Elements.ComputedStyleModel.Events.ComputedStyleChanged, this.onCSSModelChanged, this);
 
     this._updateThrottler = new Common.Throttler(100);
     this._updateWhenVisible = false;
   }
 
   /**
@@ skipping 41 matching lines @@
     if (this._updateWhenVisible)
       this.update();
   }
 
   /**
    * @param {!Common.Event} event
    */
   onCSSModelChanged(event) {
   }
 };