DevTools: support importing layer tree from trace snapshots.

Source/devtools/front_end/modules.js

 /*
  * Copyright (C) 2014 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 571 matching lines @@
         extensions: [
             {
                 type: "@WebInspector.Panel",
                 name: "layers",
                 title: "Layers",
                 order: 7,
                 className: "WebInspector.LayersPanel"
             },
             {
                 type: "@WebInspector.Revealer",
-                contextTypes: ["WebInspector.LayerTreeSnapshot"],
+                contextTypes: ["WebInspector.LayerTreeSnapshot", "WebInspector.TracingLayerSnapshot"],
                 className: "WebInspector.LayersPanel.LayerTreeRevealer"
             }
         ],
         scripts: [ "LayersPanel.js" ]
     },
     {
         name: "handler-registry",
         extensions: [
             {
                 type: "@WebInspector.ContextMenu.Provider",
                 contextTypes: ["WebInspector.UISourceCode", "WebInspector.Resource", "WebInspector.NetworkRequest", "Node"],
                 className: "WebInspector.HandlerRegistry.ContextMenuProvider"
             }
         ]
     }
 ];