Use input events to improve vsync scheduling

cc/vsync_time_source.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 CC_VSYNC_TIME_SOURCE_H_
 #define CC_VSYNC_TIME_SOURCE_H_
 
 #include "cc/cc_export.h"
 #include "cc/time_source.h"
 
 namespace cc {
 
 class CC_EXPORT VSyncClient {
  public:
   virtual void DidVSync(base::TimeTicks frame_time) = 0;
+  virtual void DidReceiveLastInputEventForVSync() = 0;
 
  protected:
   virtual ~VSyncClient() {}
 };
 
 class VSyncProvider {
  public:
   // Request to be notified of future vsync events. The notifications will be
   // delivered until they are disabled by calling this function with a null
   // client.
@@ skipping 13 matching lines @@
   virtual void setClient(TimeSourceClient* client) OVERRIDE;
   virtual void setTimebaseAndInterval(base::TimeTicks timebase,
                                       base::TimeDelta interval) OVERRIDE;
   virtual void setActive(bool active) OVERRIDE;
   virtual bool active() const OVERRIDE;
   virtual base::TimeTicks lastTickTime() OVERRIDE;
   virtual base::TimeTicks nextTickTime() OVERRIDE;
 
   // VSyncClient implementation
   virtual void DidVSync(base::TimeTicks frame_time) OVERRIDE;
+  virtual void DidReceiveLastInputEventForVSync() OVERRIDE;
+
+  // Virtual for testing.
+  virtual base::TimeTicks Now() const;
 
  protected:
   explicit VSyncTimeSource(VSyncProvider* vsync_provider);
   virtual ~VSyncTimeSource();
 
   base::TimeTicks last_tick_time_;
   base::TimeDelta interval_;
   bool active_;
   bool notification_requested_;
+  bool did_synthesize_last_vsync_;
 
   VSyncProvider* vsync_provider_;
   TimeSourceClient* client_;
 
   DISALLOW_COPY_AND_ASSIGN(VSyncTimeSource);
 };
 
 }  // namespace cc
 
 #endif  // CC_VSYNC_TIME_SOURCE_H_