Removing the TimeSource abstraction as it is not used anywhere.

cc/scheduler/time_source.h

-// Copyright 2011 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_SCHEDULER_TIME_SOURCE_H_
-#define CC_SCHEDULER_TIME_SOURCE_H_
-
-#include "base/memory/ref_counted.h"
-#include "base/time/time.h"
-#include "cc/base/cc_export.h"
-
-namespace cc {
-
-class CC_EXPORT TimeSourceClient {
- public:
-  virtual void OnTimerTick() = 0;
-
- protected:
-  virtual ~TimeSourceClient() {}
-};
-
-// An generic interface for getting a reliably-ticking timesource of
-// a specified rate.
-//
-// Be sure to call SetActive(false) before releasing your reference to the
-// timer, or it will keep on ticking!
-class CC_EXPORT TimeSource : public base::RefCounted<TimeSource> {
- public:
-  virtual void SetClient(TimeSourceClient* client) = 0;
-
-  // If transitioning from not active to active, SetActive will return the
-  // timestamp of the most recenly missed tick that did not have OnTimerTick
-  // called.
-  virtual base::TimeTicks SetActive(bool active) = 0;
-
-  virtual bool Active() const = 0;
-  virtual void SetTimebaseAndInterval(base::TimeTicks timebase,
-                                      base::TimeDelta interval) = 0;
-  virtual base::TimeTicks LastTickTime() const = 0;
-  virtual base::TimeTicks NextTickTime() const = 0;
-
- protected:
-  virtual ~TimeSource() {}
-
- private:
-  friend class base::RefCounted<TimeSource>;
-};
-
-}  // namespace cc
-
-#endif  // CC_SCHEDULER_TIME_SOURCE_H_