cc: Cleanup DelayBasedTimeSource code.

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 bc828026303bce098331606e8c675a73bf5ff110..8c97f6e20b67d292e970de193fcd57368ed68d34 100644
--- a/cc/scheduler/begin_frame_source.cc
+++ b/cc/scheduler/begin_frame_source.cc
@@ -210,12 +210,17 @@ scoped_ptr<SyntheticBeginFrameSource> SyntheticBeginFrameSource::Create(
     base::TimeDelta initial_vsync_interval) {
   scoped_ptr<DelayBasedTimeSource> time_source =
       DelayBasedTimeSource::Create(initial_vsync_interval, task_runner);
-  return make_scoped_ptr(new SyntheticBeginFrameSource(time_source.Pass()));
+  return make_scoped_ptr(
+      new SyntheticBeginFrameSource(task_runner, time_source.Pass()));
 }
 
 SyntheticBeginFrameSource::SyntheticBeginFrameSource(
+    base::SingleThreadTaskRunner* task_runner,
     scoped_ptr<DelayBasedTimeSource> time_source)
-    : BeginFrameSourceBase(), time_source_(time_source.Pass()) {
+    : BeginFrameSourceBase(),
+      task_runner_(task_runner),
+      time_source_(time_source.Pass()),
+      weak_factory_(this) {
   time_source_->SetActive(false);
   time_source_->SetClient(this);
 }
@@ -251,8 +256,11 @@ void SyntheticBeginFrameSource::OnNeedsBeginFramesChange(
   base::TimeTicks missed_tick_time =
       time_source_->SetActive(needs_begin_frames);
   if (!missed_tick_time.is_null()) {
-    CallOnBeginFrame(
-        CreateBeginFrameArgs(missed_tick_time, BeginFrameArgs::MISSED));
+    task_runner_->PostTask(
+        FROM_HERE, base::Bind(&SyntheticBeginFrameSource::CallOnBeginFrame,
+                              weak_factory_.GetWeakPtr(),
+                              CreateBeginFrameArgs(missed_tick_time,
+                                                   BeginFrameArgs::MISSED)));
   }
 }