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

components/scheduler/child/webthread_impl_for_worker_scheduler.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/webthread_impl_for_worker_scheduler.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/time/default_tick_clock.h"
 #include "components/scheduler/base/task_queue.h"
 #include "components/scheduler/child/scheduler_task_runner_delegate_impl.h"
 #include "components/scheduler/child/web_scheduler_impl.h"
 #include "components/scheduler/child/web_task_runner_impl.h"
 #include "components/scheduler/child/worker_scheduler_impl.h"
 #include "third_party/WebKit/public/platform/WebTraceLocation.h"
 
 namespace scheduler {
 
 WebThreadImplForWorkerScheduler::WebThreadImplForWorkerScheduler(
@@ skipping 15 matching lines @@
   thread_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&WebThreadImplForWorkerScheduler::RestoreTaskRunnerOnThread,
                  base::Unretained(this), &completion));
   completion.Wait();
   thread_->Stop();
 }
 
 void WebThreadImplForWorkerScheduler::InitOnThread(
     base::WaitableEvent* completion) {
-  task_runner_delegate_ =
-      SchedulerTaskRunnerDelegateImpl::Create(thread_->message_loop());
+  // TODO(alexclarke): Do we need to unify virtual time for workers and the
+  // main thread?

[Sami, 2015/10/30 11:11:20]

One issue here is that workers will see virtual time in Date.now() etc. but
their timers will fire according to wall clock time. I don't think we need to
fix that in this patch but something to be aware of.

[alex clarke (OOO till 29th), 2015/10/30 12:12:25]

Acknowledged.

+  task_runner_delegate_ = SchedulerTaskRunnerDelegateImpl::Create(
+      thread_->message_loop(), make_scoped_ptr(new base::DefaultTickClock()));
   worker_scheduler_ = WorkerScheduler::Create(task_runner_delegate_);
   worker_scheduler_->Init();
   task_runner_ = worker_scheduler_->DefaultTaskRunner();
   idle_task_runner_ = worker_scheduler_->IdleTaskRunner();
   web_scheduler_.reset(new WebSchedulerImpl(
       worker_scheduler_.get(), worker_scheduler_->IdleTaskRunner(),
       worker_scheduler_->DefaultTaskRunner(),
       worker_scheduler_->DefaultTaskRunner()));
   base::MessageLoop::current()->AddDestructionObserver(this);
   web_task_runner_ = make_scoped_ptr(new WebTaskRunnerImpl(task_runner_));
@@ skipping 39 matching lines @@
     base::MessageLoop::TaskObserver* observer) {
   worker_scheduler_->AddTaskObserver(observer);
 }
 
 void WebThreadImplForWorkerScheduler::RemoveTaskObserverInternal(
     base::MessageLoop::TaskObserver* observer) {
   worker_scheduler_->RemoveTaskObserver(observer);
 }
 
 }  // namespace scheduler