cc: Cleanup DelayBasedTimeSource code.

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 <string>
 
+#include "base/cancelable_callback.h"
 #include "base/memory/weak_ptr.h"
 #include "base/values.h"
 #include "cc/base/cc_export.h"
 
 namespace base {
 namespace trace_event {
 class TracedValue;
 }
 class SingleThreadTaskRunner;
 }
 
 namespace cc {
-
-class CC_EXPORT TimeSourceClient {
+class CC_EXPORT DelayBasedTimeSourceClient {
  public:
   virtual void OnTimerTick() = 0;
 
  protected:
-  virtual ~TimeSourceClient() {}
+  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 scoped_ptr<DelayBasedTimeSource> Create(
       base::TimeDelta interval,
       base::SingleThreadTaskRunner* task_runner) {
     return make_scoped_ptr(new DelayBasedTimeSource(interval, task_runner));
   }
 
   virtual ~DelayBasedTimeSource();
 
-  virtual void SetClient(TimeSourceClient* client);
+  void SetClient(DelayBasedTimeSourceClient* client);
 
-  // TimeSource implementation
-  virtual void SetTimebaseAndInterval(base::TimeTicks timebase,
-                                      base::TimeDelta interval);
-  base::TimeDelta Interval() const { return next_parameters_.interval; }
+  void SetTimebaseAndInterval(base::TimeTicks timebase,
+                              base::TimeDelta interval);
 
-  virtual base::TimeTicks SetActive(bool active);
-  virtual bool Active() const;
+  base::TimeDelta Interval() const;
+
+  // Returns the time for the last missed tick.
+  base::TimeTicks SetActive(bool active);
+  bool Active() const;
 
   // Get the last and next tick times. NextTickTime() returns null when
   // inactive.
-  virtual base::TimeTicks LastTickTime() const;
-  virtual base::TimeTicks NextTickTime() const;
-
-  // Virtual for testing.
-  virtual base::TimeTicks Now() const;
+  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;
 
-  base::TimeTicks NextTickTarget(base::TimeTicks now);
+ private:
+  base::TimeTicks NextTickTarget(base::TimeTicks now) const;
+
   void PostNextTickTask(base::TimeTicks now);
-  void OnTimerFired();
+  void ResetTickTask(base::TimeTicks now);
 
-  struct Parameters {
-    Parameters(base::TimeDelta interval, base::TimeTicks tick_target)
-        : interval(interval), tick_target(tick_target) {}
-    base::TimeDelta interval;
-    base::TimeTicks tick_target;
-  };
+  void OnTimerTick();
 
-  TimeSourceClient* client_;
-  base::TimeTicks last_tick_time_;
-
-  // current_parameters_ should only be written by PostNextTickTask.
-  // next_parameters_ will take effect on the next call to PostNextTickTask.
-  // Maintaining a pending set of parameters allows NextTickTime() to always
-  // reflect the actual time we expect OnTimerFired to be called.
-  Parameters current_parameters_;
-  Parameters next_parameters_;
+  DelayBasedTimeSourceClient* client_;
 
   bool active_;
 
+  base::TimeTicks timebase_;
+  base::TimeDelta interval_;
+
+  base::TimeTicks last_tick_time_;
+  base::TimeTicks next_tick_time_;
+
+  base::CancelableClosure tick_closure_;
+
   base::SingleThreadTaskRunner* task_runner_;
+
   base::WeakPtrFactory<DelayBasedTimeSource> weak_factory_;
 
- private:
   DISALLOW_COPY_AND_ASSIGN(DelayBasedTimeSource);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_DELAY_BASED_TIME_SOURCE_H_