CrOS: Look for consistency between successive vsync intervals.

ui/gl/vsync_provider.h

Index: ui/gl/vsync_provider.h
diff --git a/ui/gl/vsync_provider.h b/ui/gl/vsync_provider.h
index 5c7b2a46ed7022fca7c1357dcc1419fb7c2ffb0b..bec065ea5b22d1ccd8c1a8df60a99808f86f2aa5 100644
--- a/ui/gl/vsync_provider.h
+++ b/ui/gl/vsync_provider.h
@@ -5,6 +5,8 @@
 #ifndef UI_GL_VSYNC_PROVIDER_H_
 #define UI_GL_VSYNC_PROVIDER_H_
 
+#include <queue>
+
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/time.h"
@@ -54,6 +56,12 @@ class SyncControlVSyncProvider : public VSyncProvider {
   uint64 last_media_stream_counter_;
   base::TimeDelta last_good_interval_;
 
+  // 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);
 };