Refactoring the way begin frame sources inside scheduler work.

cc/output/vsync_parameter_observer.h

Index: cc/output/vsync_parameter_observer.h
diff --git a/cc/output/vsync_parameter_observer.h b/cc/output/vsync_parameter_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..e586925e110e5e2b1a9e3cbadbf854a76332d0c4
--- /dev/null
+++ b/cc/output/vsync_parameter_observer.h
@@ -0,0 +1,18 @@
+// Copyright 2014 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 CC_OUTPUT_VSYNC_PARAMETER_OBSERVER_H_
+#define CC_OUTPUT_VSYNC_PARAMETER_OBSERVER_H_
+
+#include "base/time/time.h"
+
+// Interface for a class which observes the parameters regarding vsync
+// information.
+class VSyncParameterObserver {
+ public:
+  virtual void OnUpdateVSyncParameters(base::TimeTicks timebase,
+                                       base::TimeDelta interval) = 0;
+};
+
+#endif  // CC_OUTPUT_VSYNC_PARAMETER_OBSERVER_H_