Make disable vsync run the renderer independently

cc/scheduler/begin_frame_source.cc

Index: cc/scheduler/begin_frame_source.cc
diff --git a/cc/scheduler/begin_frame_source.cc b/cc/scheduler/begin_frame_source.cc
index 583f0f6a6c5849dec40da4b83faf41397a066748..30916948cec360b751b158e69316c4e6617f8b3b 100644
--- a/cc/scheduler/begin_frame_source.cc
+++ b/cc/scheduler/begin_frame_source.cc
@@ -44,6 +44,10 @@ void BeginFrameObserverBase::OnBeginFrame(const BeginFrameArgs& args) {
   }
 }
 
+bool StubBeginFrameSource::IsThrottled() const {
+  return true;
+}
+
 // SyntheticBeginFrameSource ---------------------------------------------
 SyntheticBeginFrameSource::~SyntheticBeginFrameSource() = default;
 
@@ -85,6 +89,10 @@ void BackToBackBeginFrameSource::DidFinishFrame(BeginFrameObserver* obs,
   }
 }
 
+bool BackToBackBeginFrameSource::IsThrottled() const {
+  return false;
+}
+
 void BackToBackBeginFrameSource::OnTimerTick() {
   base::TimeTicks frame_time = time_source_->LastTickTime();
   base::TimeDelta default_interval = BeginFrameArgs::DefaultInterval();
@@ -165,6 +173,10 @@ void DelayBasedBeginFrameSource::RemoveObserver(BeginFrameObserver* obs) {
     time_source_->SetActive(false);
 }
 
+bool DelayBasedBeginFrameSource::IsThrottled() const {
+  return true;
+}
+
 void DelayBasedBeginFrameSource::OnTimerTick() {
   BeginFrameArgs args = CreateBeginFrameArgs(time_source_->LastTickTime(),
                                              BeginFrameArgs::NORMAL);
@@ -217,6 +229,10 @@ void ExternalBeginFrameSource::RemoveObserver(BeginFrameObserver* obs) {
   }
 }
 
+bool ExternalBeginFrameSource::IsThrottled() const {
+  return true;
+}
+
 void ExternalBeginFrameSource::OnSetBeginFrameSourcePaused(bool paused) {
   if (paused_ == paused)
     return;