DevTools: make DOMNodeIds a trivial wrapper around WeakIdentifierMap

Source/core/dom/DOMNodeIds.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DOMNodeIds_h
 #define DOMNodeIds_h
 
 #include "core/CoreExport.h"
+#include "core/dom/WeakIdentifierMap.h"
 
 namespace blink {
 
 class Node;
 
+#if !ENABLE(OILPAN)
+template<> struct WeakIdentifierMapTraits<Node> {
+    static void removedFromIdentifierMap(Node*);
+    static void addedToIdentifierMap(Node*);
+};
+#endif
+
+typedef WeakIdentifierMap<Node> WeakNodeMap;
+
 class CORE_EXPORT DOMNodeIds {
 public:
     static int idForNode(Node*);
     static Node* nodeForId(int);
 };
 
 } // namespace blink
 
 
 #endif // DOMNodeIds_h