DevTools: migrate sources navigator to shadow

BUG=726972

Review-Url: https://codereview.chromium.org/2924413002
Cr-Commit-Position: refs/heads/master@{#478745}

third_party/WebKit/Source/devtools/front_end/sources/NavigatorView.js

@@ -31,13 +31,13 @@
  */
 Sources.NavigatorView = class extends UI.VBox {
   constructor() {
-    super();
+    super(true);
     this.registerRequiredCSS('sources/navigatorView.css');
 
     this._scriptsTree = new UI.TreeOutlineInShadow();
     this._scriptsTree.registerRequiredCSS('sources/navigatorTree.css');
     this._scriptsTree.setComparator(Sources.NavigatorView._treeElementsCompare);
-    this.element.appendChild(this._scriptsTree.element);
+    this.contentElement.appendChild(this._scriptsTree.element);
     this.setDefaultFocusedElement(this._scriptsTree.element);
 
     /** @type {!Multimap<!Workspace.UISourceCode, !Sources.NavigatorUISourceCodeTreeNode>} */
@@ -51,7 +51,7 @@ Sources.NavigatorView = class extends UI.VBox {
     /** @type {!Map.<!SDK.ResourceTreeFrame, !Sources.NavigatorGroupTreeNode>} */
     this._frameNodes = new Map();
 
-    this.element.addEventListener('contextmenu', this.handleContextMenu.bind(this), false);
+    this.contentElement.addEventListener('contextmenu', this.handleContextMenu.bind(this), false);
 
     this._navigatorGroupByFolderSetting = Common.moduleSetting('navigatorGroupByFolder');
     this._navigatorGroupByFolderSetting.addChangeListener(this._groupingChanged.bind(this));

third_party/WebKit/Source/devtools/front_end/sources/SourcesNavigator.js

@@ -147,7 +147,7 @@ Sources.FilesNavigatorView = class extends Sources.NavigatorView {
     addButton.addEventListener(
         UI.ToolbarButton.Events.Click, () => Persistence.isolatedFileSystemManager.addFileSystem());
     toolbar.appendToolbarItem(addButton);
-    this.element.insertBefore(toolbar.element, this.element.firstChild);
+    this.contentElement.insertBefore(toolbar.element, this.contentElement.firstChild);
   }
 
   /**
@@ -198,7 +198,7 @@ Sources.SnippetsNavigatorView = class extends Sources.NavigatorView {
     var newButton = new UI.ToolbarButton('', 'largeicon-add', Common.UIString('New snippet'));
     newButton.addEventListener(UI.ToolbarButton.Events.Click, this._handleCreateSnippet.bind(this));
     toolbar.appendToolbarItem(newButton);
-    this.element.insertBefore(toolbar.element, this.element.firstChild);
+    this.contentElement.insertBefore(toolbar.element, this.contentElement.firstChild);
   }
 
   /**