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

blimp/engine/renderer/blimp_remote_compositor_bridge.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 BLIMP_ENGINE_RENDERER_BLIMP_REMOTE_COMPOSITOR_BRIDGE_H_
 #define BLIMP_ENGINE_RENDERER_BLIMP_REMOTE_COMPOSITOR_BRIDGE_H_
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "blimp/engine/renderer/frame_scheduler.h"
@@ skipping 26 matching lines @@
   // cc::RemoteProtoChannel::ProtoReceiver implementation.
   void OnProtoReceived(
       std::unique_ptr<cc::proto::CompositorMessage> proto) override;
 
   // FrameSchedulerClient implementation.
   void StartFrameUpdate() override;
 
   cc::RemoteProtoChannel* remote_proto_channel_;
   cc::RemoteCompositorBridgeClient* client_ = nullptr;
 
+  bool client_state_update_ack_pending_ = false;
+
   FrameScheduler scheduler_;
 
   DISALLOW_COPY_AND_ASSIGN(BlimpRemoteCompositorBridge);
 };
 
 }  // namespace engine
 }  // namespace blimp
 
 #endif  // BLIMP_ENGINE_RENDERER_BLIMP_REMOTE_COMPOSITOR_BRIDGE_H_