DevTools: avoid using stale front-end node ids.

Source/devtools/front_end/LayerTreeModel.js

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 183 matching lines @@
     /**
      * @param {!Array.<!LayerTreeAgent.Layer>} layers
      * @param {function()} callback
      */
     _resolveBackendNodeIdsForLayers: function(layers, callback)
     {
         var idsToResolve = {};
         var requestedIds = [];
         for (var i = 0; i < layers.length; ++i) {
             var backendNodeId = layers[i].backendNodeId;
-            if (!backendNodeId || this._backendNodeIdToNodeId[backendNodeId] || idsToResolve[backendNodeId])
+            if (!backendNodeId || idsToResolve[backendNodeId] ||
+                (this._backendNodeIdToNodeId[backendNodeId] && WebInspector.domAgent.nodeForId(this._backendNodeIdToNodeId[backendNodeId]))) {
                 continue;
+            }
             idsToResolve[backendNodeId] = true;
             requestedIds.push(backendNodeId);
         }
         if (!requestedIds.length) {
             callback();
             return;
         }
         WebInspector.domAgent.pushNodesByBackendIdsToFrontend(requestedIds, populateBackendNodeIdMap.bind(this));
 
         /**
@@ skipping 275 matching lines @@
 
     /**
      * @param {!LayerTreeAgent.LayerId} layerId
      * @param {!DOMAgent.Rect} clipRect
      */
     layerPainted: function(layerId, clipRect)
     {
         this._layerTreeModel._layerPainted(layerId, clipRect);
     }
 }