Blink CompositorWorker: Use CompositorElementId and CompositorIdToElementMap.

third_party/WebKit/Source/core/dom/CompositorIdToElementMap.h

+// Copyright 2016 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 CompositorIdToElementMap_h
+#define CompositorIdToElementMap_h
+
+#include "core/CoreExport.h"
+#include "platform/graphics/CompositorElementId.h"
+#include "wtf/Allocator.h"
+
+namespace blink {
+
+class Element;
+
+class CORE_EXPORT CompositorIdToElementMap {
+    STATIC_ONLY(CompositorIdToElementMap);
+public:
+    static void registerElement(Element&);
+    static Element* getById(CompositorElementId);
+};
+
+} // namespace blink
+
+
+#endif // DOMNodeIds_h