scheduler: Make virtual time expiration deterministic

third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc

 // Copyright 2014 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 "platform/scheduler/renderer/renderer_scheduler_impl.h"
 
 #include "base/bind.h"
 #include "base/debug/stack_trace.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 1840 matching lines @@
   return virtual_time_domain_.get();
 }
 
 void RendererSchedulerImpl::EnableVirtualTime() {
   GetMainThreadOnly().use_virtual_time = true;
 
   // The |unthrottled_task_runners_| are not actively managed by UpdatePolicy().
   AutoAdvancingVirtualTimeDomain* time_domain = GetVirtualTimeDomain();
   for (const scoped_refptr<TaskQueue>& task_queue : unthrottled_task_runners_)
     task_queue->SetTimeDomain(time_domain);
+  control_task_runner_->SetTimeDomain(time_domain);

[alex clarke (OOO till 29th), 2017/04/25 11:53:17]

I'm a little nervous about that, generally we don't ever expect the control task
queue to be throttled / disabled.  Do we need a second lazily created control
task queue?

[Sami, 2017/04/25 16:58:21]

That's a great point, I agree that we should be a little careful here. Added a
secondary queue instead.

 
   ForceUpdatePolicy();
 }
 
 void RendererSchedulerImpl::DisableVirtualTimeForTesting() {
   GetMainThreadOnly().use_virtual_time = false;
 
   RealTimeDomain* time_domain = real_time_domain();
   // The |unthrottled_task_runners_| are not actively managed by UpdatePolicy().
   for (const scoped_refptr<TaskQueue>& task_queue : unthrottled_task_runners_)
     task_queue->SetTimeDomain(time_domain);
+  control_task_runner_->SetTimeDomain(time_domain);
 
   ForceUpdatePolicy();
 }
 
 bool RendererSchedulerImpl::ShouldDisableThrottlingBecauseOfAudio(
     base::TimeTicks now) {
   if (!GetMainThreadOnly().last_audio_state_change)
     return false;
 
   if (GetMainThreadOnly().is_audio_playing)
@@ skipping 69 matching lines @@
     case TimeDomainType::VIRTUAL:
       return "virtual";
     default:
       NOTREACHED();
       return nullptr;
   }
 }
 
 }  // namespace scheduler
 }  // namespace blink