Implement scroll handler latency tracking

cc/base/latency_info_swap_promise_monitor.h

 // Copyright 2013 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.
 
 #include "base/compiler_specific.h"
 #include "cc/base/swap_promise_monitor.h"
 
 #ifndef CC_BASE_LATENCY_INFO_SWAP_PROMISE_MONITOR_H_
 #define CC_BASE_LATENCY_INFO_SWAP_PROMISE_MONITOR_H_
 
 namespace ui {
 struct LatencyInfo;
 }  // namespace ui
 
 namespace cc {
 
 // A LatencyInfoSwapPromiseMonitor queues a LatencyInfoSwapPromise into
 // LayerTreeHost or LayerTreeHostImpl if there is compositor state change
 // while it is being mointored.
 class CC_EXPORT LatencyInfoSwapPromiseMonitor : public SwapPromiseMonitor {
  public:
   LatencyInfoSwapPromiseMonitor(ui::LatencyInfo* latency,
                                 LayerTreeHost* layer_tree_host,
                                 LayerTreeHostImpl* layer_tree_host_impl);
   virtual ~LatencyInfoSwapPromiseMonitor();
 
   virtual void OnSetNeedsCommitOnMain() OVERRIDE;
   virtual void OnSetNeedsRedrawOnImpl() OVERRIDE;
+  virtual void OnForwardScrollUpdateToMainThreadOnImpl() OVERRIDE;
 
  private:
   ui::LatencyInfo* latency_;
 };
 
 }  // namespace cc
 
 #endif  // CC_BASE_LATENCY_INFO_SWAP_PROMISE_MONITOR_H_