DevTools: Fix bug with context menu in Layers3DView.

Source/devtools/front_end/timeline/Layers3DView.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:
  *
  *     * 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 577 matching lines @@
             if (product < 0)
                 return undefined;
         }
         return t;
     },
 
     /**
      * @param {?Event} event
      * @return {?WebInspector.Layers3DView.ActiveObject}
      */
-    _layerFromEventPoint: function(event)
+    _activeObjectFromEventPoint: function(event)
     {
         if (!this._layerTree)
             return null;
         var closestIntersectionPoint = Infinity;
         var closestLayer = null;
         var projectionMatrix = new WebKitCSSMatrix().scale(1, -1, -1).translate(-1, -1, 0).multiply(this._calculateProjectionMatrix());
         var x0 = (event.clientX - this._canvasElement.totalOffsetLeft()) * window.devicePixelRatio;
         var y0 = -(event.clientY - this._canvasElement.totalOffsetTop()) * window.devicePixelRatio;
 
         /**
@@ skipping 22 matching lines @@
 
         this._layerTree.forEachLayer(checkIntersection.bind(this));
         return closestLayer;
     },
 
     /**
      * @param {?Event} event
      */
     _onContextMenu: function(event)
     {
-        var layer = this._layerFromEventPoint(event).layer;
-        var node = layer ? layer.nodeForSelfOrAncestor() : null;
+        var activeObject = this._activeObjectFromEventPoint(event);
+        var node = activeObject && activeObject.layer && activeObject.layer.nodeForSelfOrAncestor();
         var contextMenu = new WebInspector.ContextMenu(event);
         contextMenu.appendItem("Reset view", this._transformController._resetAndNotify.bind(this._transformController), false);
         if (node)
             contextMenu.appendApplicableItems(node);
         contextMenu.show();
     },
 
     /**
      * @param {?Event} event
      */
     _onMouseMove: function(event)
     {
         if (event.which)
             return;
-        this.dispatchEventToListeners(WebInspector.Layers3DView.Events.ObjectHovered, this._layerFromEventPoint(event));
+        this.dispatchEventToListeners(WebInspector.Layers3DView.Events.ObjectHovered, this._activeObjectFromEventPoint(event));
     },
 
     /**
      * @param {?Event} event
      */
     _onMouseDown: function(event)
     {
         this._mouseDownX = event.clientX;
         this._mouseDownY = event.clientY;
     },
 
     /**
      * @param {?Event} event
      */
     _onMouseUp: function(event)
     {
         const maxDistanceInPixels = 6;
         if (this._mouseDownX && Math.abs(event.clientX - this._mouseDownX) < maxDistanceInPixels && Math.abs(event.clientY - this._mouseDownY) < maxDistanceInPixels)
-            this.dispatchEventToListeners(WebInspector.Layers3DView.Events.ObjectSelected, this._layerFromEventPoint(event));
+            this.dispatchEventToListeners(WebInspector.Layers3DView.Events.ObjectSelected, this._activeObjectFromEventPoint(event));
         delete this._mouseDownX;
         delete this._mouseDownY;
     },
 
     /**
      * @param {?Event} event
      */
     _onDoubleClick: function(event)
     {
-        var object = this._layerFromEventPoint(event);
+        var object = this._activeObjectFromEventPoint(event);
         if (object && object.layer)
             this.dispatchEventToListeners(WebInspector.Layers3DView.Events.LayerSnapshotRequested, object.layer);
         event.stopPropagation();
     },
 
     __proto__: WebInspector.VBox.prototype
 }