Add a simple scheduler for animation frames

mc/scheduler/scheduler.h

+// 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 MC_SCHEDULER_SCHEDULER_H_
+#define MC_SCHEDULER_SCHEDULER_H_
+
+#include "base/single_thread_task_runner.h"
+#include "base/time/time.h"
+#include "mc/scheduler/timer.h"
+
+namespace mc {
+
+class Scheduler : public Timer::Client {
+ public:
+  class Client {
+   public:
+    virtual void BeginFrame(base::TimeTicks frame_time,
+                            base::TimeTicks deadline) = 0;
+
+   protected:
+    virtual ~Client();
+  };
+
+  Scheduler(Client* client,
+            scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+  ~Scheduler();
+
+  void UpdateFrameDuration(base::TimeDelta estimate);
+  void UpdateVSync(const TimeInterval& vsync);
+
+  void SetNeedsFrame();
+
+ private:
+  void UpdateTimerInterval();
+  void OnTimerTick(base::TimeTicks now) override;
+
+  Client* client_;
+  Timer timer_;
+  TimeInterval vsync_;
+  base::TimeDelta frame_duration_;
+};
+}
+
+#endif  // MC_SCHEDULER_SCHEDULER_H_