DevTools: make ElementsTreeOutline shadow dom-based.

Source/devtools/front_end/ui/RootView.js

 // Copyright 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.
 
 /**
  * @constructor
  * @extends {WebInspector.VBox}
  */
 WebInspector.RootView = function()
 {
     WebInspector.VBox.call(this);
     this.markAsRoot();
-    this.element.classList.add("root-view");
+    this.element.classList.add("root-view", "component-root");
     this.element.setAttribute("spellcheck", false);
     window.addEventListener("resize", this.doResize.bind(this), false);
 }
 
 WebInspector.RootView.prototype = {
     attachToBody: function()
     {
         this.doResize();
         this.show(document.body);
     },
 
     doResize: function()
     {
         var size = this.constraints().minimum;
         var zoom = WebInspector.zoomManager.zoomFactor();
         var right = Math.min(0, window.innerWidth - size.width / zoom);
         this.element.style.marginRight = right + "px";
         var bottom = Math.min(0, window.innerHeight - size.height / zoom);
         this.element.style.marginBottom = bottom + "px";
         WebInspector.VBox.prototype.doResize.call(this);
     },
 
     __proto__: WebInspector.VBox.prototype
 }