cc: Add support for sending BeginFrames for video.

cc/trees/thread_proxy.cc

Index: cc/trees/thread_proxy.cc
diff --git a/cc/trees/thread_proxy.cc b/cc/trees/thread_proxy.cc
index beaf92f50b474d3491752d578936d817ddb380a6..db4091cbc0724efc2e305a5d7832a4f7b2425b31 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -401,6 +401,15 @@ void ThreadProxy::SetNeedsCommitOnImplThread() {
   impl().scheduler->SetNeedsCommit();
 }
 
+void ThreadProxy::SetVideoNeedsBeginFrames(bool needs_begin_frames) {
+  TRACE_EVENT1("cc", "ThreadProxy::SetVideoNeedsBeginFrames",
+               "needs_begin_frames", needs_begin_frames);
+  DCHECK(IsImplThread());
+  // In tests the layer tree is destroyed after the scheduler is.
+  if (impl().scheduler)
+    impl().scheduler->SetVideoNeedsBeginFrames(needs_begin_frames);
+}
+
 void ThreadProxy::PostAnimationEventsToMainThreadOnImplThread(
     scoped_ptr<AnimationEventsVector> events) {
   TRACE_EVENT0("cc",