Revert 210101 "cc: Fix and simplify DelayBasedTimeSource"

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 "base/memory/weak_ptr.h"
 #include "cc/base/cc_export.h"
 #include "cc/scheduler/time_source.h"
@@ skipping 29 matching lines @@
 
  protected:
   DelayBasedTimeSource(base::TimeDelta interval,
                        base::SingleThreadTaskRunner* task_runner);
   virtual ~DelayBasedTimeSource();
 
   base::TimeTicks NextTickTarget(base::TimeTicks now);
   void PostNextTickTask(base::TimeTicks now);
   void OnTimerFired();
 
+  enum State {
+    STATE_INACTIVE,
+    STATE_STARTING,
+    STATE_ACTIVE,
+  };
+
   struct Parameters {
     Parameters(base::TimeDelta interval, base::TimeTicks tick_target)
         : interval(interval), tick_target(tick_target) {}
     base::TimeDelta interval;
     base::TimeTicks tick_target;
   };
 
   TimeSourceClient* client_;
+  bool has_tick_target_;
   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_;
 
-  bool active_;
+  State state_;
 
   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_