Allow tasks scheduled for the instant virtual time budges expires to run

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 fa6a06c86d0821630db268290ca2b6f145301b08..8d158fcc5e6e21dff8ada450249467a6e78d5ecd 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
@@ -219,6 +219,7 @@ RendererSchedulerImpl::MainThreadOnly::MainThreadOnly(
       in_idle_period_for_testing(false),
       use_virtual_time(false),
       is_audio_playing(false),
+      virtual_time_suspended(false),
       rail_mode_observer(nullptr),
       wake_up_budget_pool(nullptr),
       task_duration_per_queue_type_histogram(base::Histogram::FactoryGet(
@@ -370,6 +371,8 @@ scoped_refptr<TaskQueue> RendererSchedulerImpl::NewTimerTaskQueue(
       TimeDomainType::THROTTLED) {
     task_queue_throttler_->IncreaseThrottleRefCount(timer_task_queue.get());
   }
+  if (GetMainThreadOnly().virtual_time_suspended)

[altimin, 2017/05/31 11:44:06]

Is virtual_time_expired a better name?

[alex clarke (OOO till 29th), 2017/05/31 15:11:36]

virtual_time_paused is possibly the most accurate name.

[alex clarke (OOO till 29th), 2017/05/31 16:48:48]

I understand Alexander has a strong preference for _expired due to the budget
however I respectfully disagree. This state is entered when
WebViewSchedulerImpl::allow_virtual_time_to_advance_ is false and
WebViewSchedulerImpl::virtual_time_ is true.  That only happens when we are in
VirtualTimePolicy::PAUSE (hence my preferred name).

Now it is true that the layer above sets the policy to VirtualTimePolicy::PAUSE
when the virtual time budget expires, but that concept doesn't exist at this
level.

[altimin, 2017/05/31 16:51:24]

Yes, it makes sense, thanks for the explanation.

+    timer_task_queue->InsertFence(TaskQueue::InsertFencePosition::NOW);
   timer_task_queue->AddTaskObserver(
       &GetMainThreadOnly().timer_task_cost_estimator);
   AddQueueToWakeUpBudgetPool(timer_task_queue.get());
@@ -1413,6 +1416,22 @@ void RendererSchedulerImpl::ResumeTimerQueue() {
   ForceUpdatePolicy();
 }
 
+void RendererSchedulerImpl::InsertTimerFence() {
+  GetMainThreadOnly().virtual_time_suspended = true;
+  for (const auto& pair : timer_task_runners_) {
+    DCHECK(!task_queue_throttler_->IsThrottled(pair.first.get()));

[altimin, 2017/05/31 11:44:06]

Also DCHECK for not having a fence already and virtual time not being suspended
twice?

[alex clarke (OOO till 29th), 2017/05/31 15:11:36]

Done.

+    pair.first->InsertFence(TaskQueue::InsertFencePosition::NOW);
+  }
+}
+
+void RendererSchedulerImpl::RemoveTimerFence() {
+  GetMainThreadOnly().virtual_time_suspended = false;
+  for (const auto& pair : timer_task_runners_) {
+    DCHECK(!task_queue_throttler_->IsThrottled(pair.first.get()));
+    pair.first->RemoveFence();
+  }
+}
+
 void RendererSchedulerImpl::SetTimerQueueSuspensionWhenBackgroundedEnabled(
     bool enabled) {
   // Note that this will only take effect for the next backgrounded signal.
@@ -1527,6 +1546,8 @@ RendererSchedulerImpl::AsValueLocked(base::TimeTicks optional_now) const {
                        .timer_task_cost_estimator.expected_task_duration()
                        .InMillisecondsF());
   state->SetBoolean("is_audio_playing", GetMainThreadOnly().is_audio_playing);
+  state->SetBoolean("virtual_time_suspended",
+                    GetMainThreadOnly().virtual_time_suspended);
 
   state->BeginDictionary("web_view_schedulers");
   for (WebViewSchedulerImpl* web_view_scheduler :