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 34 matching lines @@
   INPUT_EVENT_LATENCY_TERMINATED_MOUSE_COMPONENT,
   // Timestamp when the touch event is acked from renderer and it does not
   // cause any rendering schedueld and does not generate any gesture event.
   INPUT_EVENT_LATENCY_TERMINATED_TOUCH_COMPONENT,
   // Timestamp when the gesture event is acked from renderer, and it does not
   // cause any rendering schedueld.
   INPUT_EVENT_LATENCY_TERMINATED_GESTURE_COMPONENT,
   // Timestamp when the frame is swapped (i.e. when the rendering caused by
   // input event actually takes effect).
   INPUT_EVENT_LATENCY_TERMINATED_FRAME_SWAP_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 44 matching lines @@
   LatencyMap latency_components;
   // The unique id for matching the ASYNC_BEGIN/END trace event.
   int64 trace_id;
   // Whether a terminal component has been added.
   bool terminated;
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_LATENCY_INFO_H_