[DevTools] Make resource tree model optional

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

 /*
  * Copyright (C) 2007, 2008 Apple Inc.  All rights reserved.
  * Copyright (C) 2008 Matt Lilek <webkit@mattlilek.com>
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * 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
@@ skipping 620 matching lines @@
     },
 
     /**
      * @param {!Element} anchor
      * @param {!WebInspector.Popover} popover
      */
     _showPopover: function(anchor, popover)
     {
         var listItem = anchor.enclosingNodeOrSelfWithNodeName("li");
         var node = /** @type {!WebInspector.ElementsTreeElement} */ (listItem.treeElement).node();
-        this._loadDimensionsForNode(node, WebInspector.DOMPresentationUtils.buildImagePreviewContents.bind(WebInspector.DOMPresentationUtils, node.target(), anchor.href, true, showPopover));
+        var resourceTreeModel = WebInspector.ResourceTreeModel.fromTarget(node.target());
+        if (!resourceTreeModel)
+            return;
+        this._loadDimensionsForNode(node, WebInspector.DOMPresentationUtils.buildImagePreviewContents.bind(WebInspector.DOMPresentationUtils, resourceTreeModel, anchor.href, true, showPopover));
 
         /**
          * @param {!Element=} contents
          */
         function showPopover(contents)
         {
             if (!contents)
                 return;
             popover.setCanShrink(false);
             popover.showForAnchor(contents, anchor);
@@ skipping 1130 matching lines @@
             if (node) {
                 this.treeOutline._selectedDOMNode = node;
                 this.treeOutline._selectedNodeChanged();
             }
         }
         return true;
     },
 
     __proto__: TreeElement.prototype
 }