Implement scroll handler latency tracking

cc/base/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.
 
 #ifndef CC_BASE_SWAP_PROMISE_MONITOR_H_
 #define CC_BASE_SWAP_PROMISE_MONITOR_H_
 
 #include "cc/base/cc_export.h"
 
 namespace cc {
@@ skipping 15 matching lines @@
   // If the monitor lives on the main thread, pass in layer_tree_host
   // and set layer_tree_host_impl to NULL.
   // If the monitor lives on the impl thread, pass in layer_tree_host_impl
   // and set layer_tree_host to NULL.
   SwapPromiseMonitor(LayerTreeHost* layer_tree_host,
                      LayerTreeHostImpl* layer_tree_host_impl);
   virtual ~SwapPromiseMonitor();
 
   virtual void OnSetNeedsCommitOnMain() = 0;
   virtual void OnSetNeedsRedrawOnImpl() = 0;
+  virtual void OnForwardScrollUpdateToMainThreadOnImpl() = 0;
 
  protected:
   LayerTreeHost* layer_tree_host_;
   LayerTreeHostImpl* layer_tree_host_impl_;
 };
 
 }  // namespace cc
 
 #endif  // CC_BASE_SWAP_PROMISE_MONITOR_H_