cc: Send all begin frames using a PostTask.

cc/trees/single_thread_proxy.cc

Index: cc/trees/single_thread_proxy.cc
diff --git a/cc/trees/single_thread_proxy.cc b/cc/trees/single_thread_proxy.cc
index 37baa50f67b25d9d7faf17c595c3a31cbd40d44f..3aecb9ccee2601ee6246d8596ccd387b51bfbe6e 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -80,14 +80,12 @@ void SingleThreadProxy::Start(
       if (!scheduler_settings.throttle_frame_production) {
         // Unthrottled source takes precedence over external sources.
         unthrottled_begin_frame_source_.reset(new BackToBackBeginFrameSource(
-            base::MakeUnique<DelayBasedTimeSource>(
-                task_runner_provider_->MainThreadTaskRunner())));
+            task_runner_provider_->MainThreadTaskRunner()));
         frame_source = unthrottled_begin_frame_source_.get();
       }
       if (!frame_source) {
         synthetic_begin_frame_source_.reset(new DelayBasedBeginFrameSource(
-            base::MakeUnique<DelayBasedTimeSource>(
-                task_runner_provider_->MainThreadTaskRunner())));
+            task_runner_provider_->MainThreadTaskRunner()));
         frame_source = synthetic_begin_frame_source_.get();
       }
     }
@@ -377,8 +375,8 @@ void SingleThreadProxy::SetMutator(std::unique_ptr<LayerTreeMutator> mutator) {
 }
 
 void SingleThreadProxy::OnCanDrawStateChanged(bool can_draw) {
-  TRACE_EVENT1(
-      "cc", "SingleThreadProxy::OnCanDrawStateChanged", "can_draw", can_draw);
+  TRACE_EVENT1("cc", "SingleThreadProxy::OnCanDrawStateChanged", "can_draw",
+               can_draw);
   DCHECK(task_runner_provider_->IsImplThread());
   if (scheduler_on_impl_thread_)
     scheduler_on_impl_thread_->SetCanDraw(can_draw);
@@ -447,7 +445,9 @@ void SingleThreadProxy::PostAnimationEventsToMainThreadOnImplThread(
   layer_tree_host_->SetAnimationEvents(std::move(events));
 }
 
-bool SingleThreadProxy::IsInsideDraw() { return inside_draw_; }
+bool SingleThreadProxy::IsInsideDraw() {
+  return inside_draw_;
+}
 
 void SingleThreadProxy::DidActivateSyncTree() {
   // Synchronously call to CommitComplete. Resetting
@@ -600,8 +600,7 @@ bool SingleThreadProxy::SupportsImplScrolling() const {
 
 bool SingleThreadProxy::ShouldComposite() const {
   DCHECK(task_runner_provider_->IsImplThread());
-  return layer_tree_host_impl_->visible() &&
-         layer_tree_host_impl_->CanDraw();
+  return layer_tree_host_impl_->visible() && layer_tree_host_impl_->CanDraw();
 }
 
 void SingleThreadProxy::ScheduleRequestNewOutputSurface() {
@@ -737,13 +736,13 @@ void SingleThreadProxy::WillBeginImplFrame(const BeginFrameArgs& args) {
 void SingleThreadProxy::ScheduledActionSendBeginMainFrame(
     const BeginFrameArgs& begin_frame_args) {
   TRACE_EVENT0("cc", "SingleThreadProxy::ScheduledActionSendBeginMainFrame");
-  // Although this proxy is single-threaded, it's problematic to synchronously
-  // have BeginMainFrame happen after ScheduledActionSendBeginMainFrame.  This
-  // could cause a commit to occur in between a series of SetNeedsCommit calls
-  // (i.e. property modifications) causing some to fall on one frame and some to
-  // fall on the next.  Doing it asynchronously instead matches the semantics of
-  // ThreadProxy::SetNeedsCommit where SetNeedsCommit will not cause a
-  // synchronous commit.
+// Although this proxy is single-threaded, it's problematic to synchronously
+// have BeginMainFrame happen after ScheduledActionSendBeginMainFrame.  This
+// could cause a commit to occur in between a series of SetNeedsCommit calls
+// (i.e. property modifications) causing some to fall on one frame and some to
+// fall on the next.  Doing it asynchronously instead matches the semantics of
+// ThreadProxy::SetNeedsCommit where SetNeedsCommit will not cause a
+// synchronous commit.
 #if DCHECK_IS_ON()
   DCHECK(inside_impl_frame_)
       << "BeginMainFrame should only be sent inside a BeginImplFrame";
@@ -787,8 +786,8 @@ void SingleThreadProxy::BeginMainFrame(const BeginFrameArgs& begin_frame_args) {
   }
 
   if (layer_tree_host_->output_surface_lost()) {
-    TRACE_EVENT_INSTANT0(
-        "cc", "EarlyOut_OutputSurfaceLost", TRACE_EVENT_SCOPE_THREAD);
+    TRACE_EVENT_INSTANT0("cc", "EarlyOut_OutputSurfaceLost",
+                         TRACE_EVENT_SCOPE_THREAD);
     BeginMainFrameAbortedOnImplThread(
         CommitEarlyOutReason::ABORTED_OUTPUT_SURFACE_LOST);
     return;