cc: Make BackToBackBeginFrameSource a SyntheticBeginFrameSource.

cc/scheduler/delay_based_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_DELAY_BASED_TIME_SOURCE_H_
 #define CC_SCHEDULER_DELAY_BASED_TIME_SOURCE_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 18 matching lines @@
 
  protected:
   virtual ~DelayBasedTimeSourceClient() {}
 };
 
 // This timer implements a time source that achieves the specified interval
 // in face of millisecond-precision delayed callbacks and random queueing
 // delays. DelayBasedTimeSource uses base::TimeTicks::Now as its timebase.
 class CC_EXPORT DelayBasedTimeSource {
  public:
-  static std::unique_ptr<DelayBasedTimeSource> Create(
-      base::TimeDelta interval,
-      base::SingleThreadTaskRunner* task_runner) {
-    return base::WrapUnique(new DelayBasedTimeSource(interval, task_runner));
-  }
-
+  explicit DelayBasedTimeSource(base::SingleThreadTaskRunner* task_runner);
   virtual ~DelayBasedTimeSource();
 
   void SetClient(DelayBasedTimeSourceClient* client);
 
   void SetTimebaseAndInterval(base::TimeTicks timebase,
                               base::TimeDelta interval);
 
   base::TimeDelta Interval() const;
 
   void SetActive(bool active);
   bool Active() const;
 
   // Get the last and next tick times. NextTickTime() returns null when
   // inactive.
   base::TimeTicks LastTickTime() const;
   base::TimeTicks NextTickTime() const;
 
   virtual void AsValueInto(base::trace_event::TracedValue* dict) const;
 
  protected:
-  DelayBasedTimeSource(base::TimeDelta interval,
-                       base::SingleThreadTaskRunner* task_runner);
-
   // Virtual for testing.
   virtual base::TimeTicks Now() const;
   virtual std::string TypeString() const;
 
  private:
   void PostNextTickTask(base::TimeTicks now);
   void ResetTickTask(base::TimeTicks now);
 
   void OnTimerTick();
 
@@ skipping 12 matching lines @@
   base::SingleThreadTaskRunner* task_runner_;
 
   base::WeakPtrFactory<DelayBasedTimeSource> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DelayBasedTimeSource);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_DELAY_BASED_TIME_SOURCE_H_