Implement scroll handler latency tracking

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index 96e580fc16a4cffdb186cefdf091cec3047fabe7..273b79bbe359464b7bd5a4ae433fd38269b366eb 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -316,6 +316,7 @@ class CC_EXPORT LayerTreeHostImpl
   bool scroll_affects_scroll_handler() const {
     return scroll_affects_scroll_handler_;
   }
+  void QueueScrollUpdateLatencyInfo(const ui::LatencyInfo& latency_info);

[danakj, 2014/07/08 16:49:07]

this should be QueueSwapPromiseForMainThreadScrollUpdate

[Sami, 2014/07/09 13:28:55]

Done.

 
   bool IsCurrentlyScrolling() const;
 
@@ -549,6 +550,7 @@ class CC_EXPORT LayerTreeHostImpl
   void MarkUIResourceNotEvicted(UIResourceId uid);
 
   void NotifySwapPromiseMonitorsOfSetNeedsRedraw();
+  void NotifySwapPromiseMonitorsOfForwardingToMainThread();
 
   typedef base::hash_map<UIResourceId, UIResourceData>
       UIResourceMap;
@@ -595,6 +597,7 @@ class CC_EXPORT LayerTreeHostImpl
   bool wheel_scrolling_;
   bool scroll_affects_scroll_handler_;
   int scroll_layer_id_when_mouse_over_scrollbar_;
+  std::vector<ui::LatencyInfo> scroll_update_latency_infos_;

[danakj, 2014/07/08 16:49:07]

ScopedPtrVector<SwapPromise> swap_promises_for_main_thread_scroll_update_

[Sami, 2014/07/09 13:28:55]

Done.

 
   bool tile_priorities_dirty_;