Fix race conditions in window snapshot code.

ui/events/latency_info.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 UI_EVENTS_LATENCY_INFO_H_
 #define UI_EVENTS_LATENCY_INFO_H_
 
 #include <map>
 #include <utility>
 
@@ skipping 14 matching lines @@
   // is the same as INPUT_EVENT_LATENCY_RWH_COMPONENT.
   INPUT_EVENT_LATENCY_SCROLL_UPDATE_RWH_COMPONENT,
   // The original timestamp of the touch event which converts to scroll update.
   INPUT_EVENT_LATENCY_SCROLL_UPDATE_ORIGINAL_COMPONENT,
   // Original timestamp for input event (e.g. timestamp from kernel).
   INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT,
   // Timestamp when the UI event is created.
   INPUT_EVENT_LATENCY_UI_COMPONENT,
   // Timestamp when the event is acked from renderer. This is currently set
   // only for touch events.
-  INPUT_EVENT_LATENCY_ACKED_COMPONENT
+  INPUT_EVENT_LATENCY_ACKED_COMPONENT,
+  // Frame number when a window snapshot was requested. The snapshot
+  // is taken when the rendering results actually reach the screen.
+  WINDOW_SNAPSHOT_FRAME_NUMBER_COMPONENT
 };
 
 struct EVENTS_EXPORT LatencyInfo {
   struct LatencyComponent {
     // Nondecreasing number that can be used to determine what events happened
     // in the component at the time this struct was sent on to the next
     // component.
     int64 sequence_number;
     // Average time of events that happened in this component.
     base::TimeTicks event_time;
@@ skipping 41 matching lines @@
 
   LatencyMap latency_components;
 
   // This represents the final time that a frame is displayed it.
   base::TimeTicks swap_timestamp;
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_LATENCY_INFO_H_