DevTools: make DOMNodeIds a trivial wrapper around WeakIdentifierMap

Source/core/dom/WeakNodeMap.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 WeakNodeMap_h
-#define WeakNodeMap_h
-
-// Oilpan supports weak maps, so we no longer need WeakNodeMap.
-#if !ENABLE(OILPAN)
-
-#include "core/dom/Node.h"
-#include "core/dom/WeakIdentifierMap.h"
-
-namespace blink {
-
-template<> struct WeakIdentifierMapTraits<Node> {
-    static void removedFromIdentifierMap(Node* node) { node->clearFlag(Node::HasWeakReferencesFlag); }
-    static void addedToIdentifierMap(Node* node) { node->setFlag(Node::HasWeakReferencesFlag); }
-};
-
-typedef WeakIdentifierMap<Node> WeakNodeMap;
-
-} // namespace blink
-
-#endif // !ENABLE(OILPAN)
-
-#endif // WeakNodeMap_h