Adds a flag to support "Virtual Time" to the blink scheduler

components/scheduler/child/scheduler_helper.h

 // Copyright 2015 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 COMPONENTS_SCHEDULER_CHILD_SCHEDULER_HELPER_H_
 #define COMPONENTS_SCHEDULER_CHILD_SCHEDULER_HELPER_H_
 
+#include "base/time/tick_clock.h"
 #include "components/scheduler/base/task_queue_manager.h"
 #include "components/scheduler/base/task_queue_selector.h"
 #include "components/scheduler/scheduler_export.h"
 
 namespace base {
 class TickClock;
 }
 
 namespace scheduler {
 
@@ skipping 56 matching lines @@
     virtual void OnUnregisterTaskQueue(
         const scoped_refptr<TaskQueue>& queue) = 0;
   };
 
   // Called once to set the Observer. This function is called on the main
   // thread. If |observer| is null, then no callbacks will occur.
   // Note |observer| is expected to outlive the SchedulerHelper.
   void SetObserver(Observer* observer);
 
   // Accessor methods.
-  base::TimeTicks Now() const;
+  base::TickClock* tick_clock() const;
   base::TimeTicks NextPendingDelayedTaskRunTime() const;
   bool GetAndClearSystemIsQuiescentBit();
 
   // Test helpers.
-  void SetTimeSourceForTesting(scoped_ptr<base::TickClock> time_source);
   void SetWorkBatchSizeForTesting(size_t work_batch_size);
   TaskQueueManager* GetTaskQueueManagerForTesting();
 
  private:
   friend class SchedulerHelperTest;
 
   base::ThreadChecker thread_checker_;
   scoped_refptr<SchedulerTaskRunnerDelegate> main_task_runner_;
   scoped_ptr<TaskQueueManager> task_queue_manager_;
   scoped_refptr<TaskQueue> control_task_runner_;
   scoped_refptr<TaskQueue> control_after_wakeup_task_runner_;
   scoped_refptr<TaskQueue> default_task_runner_;
 
-  scoped_ptr<base::TickClock> time_source_;
-
   Observer* observer_;  // NOT OWNED
   const char* tracing_category_;
   const char* disabled_by_default_tracing_category_;
 
   DISALLOW_COPY_AND_ASSIGN(SchedulerHelper);
 };
 
 }  // namespace scheduler
 
 #endif  // COMPONENTS_SCHEDULER_CHILD_SCHEDULER_HELPER_H_