scheduler: Make virtual time expiration deterministic

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

Index: third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc b/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
index 4ae63b510f0ea3f368b47e6f97ddafc908e63ece..61c0bfdf03629b2e06b5d8c73364f10bd2f41de6 100644
--- a/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
+++ b/third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc
@@ -1858,6 +1858,7 @@ void RendererSchedulerImpl::EnableVirtualTime() {
   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();
 }
@@ -1869,6 +1870,7 @@ void RendererSchedulerImpl::DisableVirtualTimeForTesting() {
   // 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();
 }