SyncControlVSyncProvider: throttle messages when MSC=0

ui/gl/sync_control_vsync_provider.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_GL_SYNC_CONTROL_VSYNC_PROVIDER_H_
 #define UI_GL_SYNC_CONTROL_VSYNC_PROVIDER_H_
 
 #include <queue>
 
 #include "ui/gfx/vsync_provider.h"
@@ skipping 13 matching lines @@
   virtual bool GetSyncValues(int64* system_time,
                              int64* media_stream_counter,
                              int64* swap_buffer_counter) = 0;
 
   virtual bool GetMscRate(int32* numerator, int32* denominator) = 0;
 
  private:
   base::TimeTicks last_timebase_;
   uint64 last_media_stream_counter_;
   base::TimeDelta last_good_interval_;
+  bool invalid_msc_;
 
   // A short history of the last few computed intervals.
   // We use this to filter out the noise in the computation resulting
   // from configuration change (monitor reconfiguration, moving windows
   // between monitors, suspend and resume, etc.).
   std::queue<base::TimeDelta> last_computed_intervals_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncControlVSyncProvider);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GL_SYNC_CONTROL_VSYNC_PROVIDER_H_