cc/blimp: Add synchronization for scroll/scale state.

cc/blimp/compositor_state_deserializer_client.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 CC_BLIMP_COMPOSITOR_STATE_DESERIALIZER_CLIENT_H_
-#define CC_BLIMP_COMPOSITOR_STATE_DESERIALIZER_CLIENT_H_
-
-#include "base/macros.h"
-#include "cc/base/cc_export.h"
-
-namespace gfx {
-class ScrollOffset;
-}  // namespace gfx
-
-namespace cc {
-
-class CC_EXPORT CompositorStateDeserializerClient {
- public:
-  virtual ~CompositorStateDeserializerClient() {}
-
-  // Returns true if the given scroll offset update received from the engine
-  // should be ignored.
-  virtual bool ShouldRetainClientScroll(
-      int engine_layer_id,
-      const gfx::ScrollOffset& new_offset) = 0;
-
-  // Returns true if the given page scale update from the engine should be
-  // ignored.
-  virtual bool ShouldRetainClientPageScale(float new_page_scale) = 0;
-};
-
-}  // namespace cc
-
-#endif  // CC_BLIMP_COMPOSITOR_STATE_DESERIALIZER_CLIENT_H_