Animations: Introduce compositor AnimationPlayer and AnimationTimeline.

public/platform/WebCompositorAnimationPlayerClient.h

+// Copyright 2015 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 WebCompositorAnimationPlayerClient_h
+#define WebCompositorAnimationPlayerClient_h
+
+namespace blink {
+
+class WebCompositorAnimationPlayer;
+
+// A client for compositor representation of AnimationPlayer.
+class WebCompositorAnimationPlayerClient {
+public:
+    virtual ~WebCompositorAnimationPlayerClient() { }
+
+    virtual WebCompositorAnimationPlayer* compositorPlayer() const = 0;
+};
+
+} // namespace blink
+
+#endif // WebCompositorAnimationPlayerClient_h