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

components/scheduler/child/scheduler_helper.cc

 // 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.
 
 #include "components/scheduler/child/scheduler_helper.h"
 
 #include "base/time/default_tick_clock.h"
 #include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_argument.h"
 #include "components/scheduler/base/task_queue_impl.h"
@@ skipping 16 matching lines @@
           TaskQueue::Spec("control_tq")
               .SetWakeupPolicy(TaskQueue::WakeupPolicy::DONT_WAKE_OTHER_QUEUES)
               .SetShouldNotifyObservers(false))),
       control_after_wakeup_task_runner_(NewTaskQueue(
           TaskQueue::Spec("control_after_wakeup_tq")
               .SetPumpPolicy(TaskQueue::PumpPolicy::AFTER_WAKEUP)
               .SetWakeupPolicy(TaskQueue::WakeupPolicy::DONT_WAKE_OTHER_QUEUES)
               .SetShouldNotifyObservers(false))),
       default_task_runner_(NewTaskQueue(TaskQueue::Spec("default_tq")
                                             .SetShouldMonitorQuiescence(true))),
-      time_source_(new base::DefaultTickClock),
       observer_(nullptr),
       tracing_category_(tracing_category),
       disabled_by_default_tracing_category_(
           disabled_by_default_tracing_category) {
   control_task_runner_->SetQueuePriority(TaskQueue::CONTROL_PRIORITY);
   control_after_wakeup_task_runner_->SetQueuePriority(
       TaskQueue::CONTROL_PRIORITY);
 
   task_queue_manager_->SetWorkBatchSize(4);
 
@@ skipping 24 matching lines @@
 }
 
 scoped_refptr<TaskQueue> SchedulerHelper::ControlTaskRunner() {
   return control_task_runner_;
 }
 
 scoped_refptr<TaskQueue> SchedulerHelper::ControlAfterWakeUpTaskRunner() {
   return control_after_wakeup_task_runner_;
 }
 
-void SchedulerHelper::SetTimeSourceForTesting(
-    scoped_ptr<base::TickClock> time_source) {
-  CheckOnValidThread();
-  time_source_ = time_source.Pass();
-}
-
 void SchedulerHelper::SetWorkBatchSizeForTesting(size_t work_batch_size) {
   CheckOnValidThread();
   DCHECK(task_queue_manager_.get());
   task_queue_manager_->SetWorkBatchSize(work_batch_size);
 }
 
 TaskQueueManager* SchedulerHelper::GetTaskQueueManagerForTesting() {
   CheckOnValidThread();
   return task_queue_manager_.get();
 }
 
 base::TimeTicks SchedulerHelper::Now() const {
-  return time_source_->NowTicks();
+  return task_queue_manager_->tick_clock()->NowTicks();
+}
+
+base::TickClock* SchedulerHelper::tick_clock() const {
+  return task_queue_manager_->tick_clock();
 }
 
 base::TimeTicks SchedulerHelper::NextPendingDelayedTaskRunTime() const {
   CheckOnValidThread();
   DCHECK(task_queue_manager_.get());
   return task_queue_manager_->NextPendingDelayedTaskRunTime();
 }
 
 bool SchedulerHelper::GetAndClearSystemIsQuiescentBit() {
   CheckOnValidThread();
@@ skipping 22 matching lines @@
   task_queue_manager_->SetObserver(this);
 }
 
 void SchedulerHelper::OnUnregisterTaskQueue(
     const scoped_refptr<internal::TaskQueueImpl>& queue) {
   if (observer_)
     observer_->OnUnregisterTaskQueue(queue);
 }
 
 }  // namespace scheduler