[DevTools] Make resource tree model optional

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

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  * 1. Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *
@@ skipping 172 matching lines @@
         return !uiSourceCode.isFromServiceProject();
     },
 
     /**
      * @param {!WebInspector.UISourceCode} uiSourceCode
      * @return {?WebInspector.ResourceTreeFrame}
      */
     _uiSourceCodeFrame: function(uiSourceCode)
     {
         var target = WebInspector.NetworkProject.targetForProject(uiSourceCode.project());
-        if (!target)
+        var resourceTreeModel = target && WebInspector.ResourceTreeModel.fromTarget(target);
+        if (!resourceTreeModel)
             return null;
-        return WebInspector.NetworkProject.frameForProject(uiSourceCode.project()) || target.resourceTreeModel.mainFrame;
+        return WebInspector.NetworkProject.frameForProject(uiSourceCode.project()) || resourceTreeModel.mainFrame;
     },
 
     /**
      * @param {!WebInspector.UISourceCode} uiSourceCode
      */
     _addUISourceCode: function(uiSourceCode)
     {
         if (!this.accept(uiSourceCode))
             return;
 
@@ skipping 1358 matching lines @@
     {
         if (this._treeElement)
             return this._treeElement;
         this._treeElement = new WebInspector.NavigatorFolderTreeElement(this._navigatorView, this._type, this._title, this._hoverCallback);
         this._treeElement.setNode(this);
         return this._treeElement;
     },
 
     __proto__: WebInspector.NavigatorTreeNode.prototype
 }