Implement view port for allocation view

Source/devtools/front_end/HeapSnapshotView.js

 /*
  * Copyright (C) 2011 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 753 matching lines @@
     {
         var selectedNode = event.target.selectedNode;
         this._setRetainmentDataGridSource(selectedNode);
         this._inspectedObjectChanged(event);
     },
 
     _onSelectAllocationNode: function(event)
     {
         var selectedNode = event.target.selectedNode;
         this._constructorsDataGrid.setAllocationNodeId(selectedNode.allocationNodeId());
+        this._setRetainmentDataGridSource(null);
     },
 
     _inspectedObjectChanged: function(event)
     {
         var selectedNode = event.target.selectedNode;
         if (!this._profile.fromFile() && selectedNode instanceof WebInspector.HeapSnapshotGenericObjectNode)
             ConsoleAgent.addInspectedHeapObject(selectedNode.snapshotNodeId);
     },
 
     /**
@@ skipping 1389 matching lines @@
         if (color)
             swatchDiv.style.backgroundColor = color;
         else
             swatchDiv.classList.add("heap-snapshot-stats-empty-swatch");
         nameDiv.textContent = name;
         sizeDiv.textContent = WebInspector.UIString("%s KB", Number.withThousandsSeparator(Math.round(value / 1024)));
     },
 
     __proto__: WebInspector.VBox.prototype
 }