cc: Introduce forward_begin_frames_to_children and use_external_begin_frame_source

cc/test/layer_tree_test.cc

Index: cc/test/layer_tree_test.cc
diff --git a/cc/test/layer_tree_test.cc b/cc/test/layer_tree_test.cc
index fd343db0a977840919b31477c49908dec7d1eccd..4e7d0f39b3578b86d5ec4c5f6c7a57662736b6cc 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -608,8 +608,7 @@ void LayerTreeTest::DoBeginTest() {
   client_ = LayerTreeHostClientForTesting::Create(this);
 
   scoped_ptr<ExternalBeginFrameSourceForTest> external_begin_frame_source;
-  if (settings_.begin_frame_scheduling_enabled &&
-      settings_.throttle_frame_production) {
+  if (settings_.begin_frame_receiver && settings_.throttle_frame_production) {
     external_begin_frame_source.reset(
         new ExternalBeginFrameSourceForTest(settings_.refresh_rate));
     external_begin_frame_source_ = external_begin_frame_source.get();
@@ -791,8 +790,7 @@ scoped_ptr<OutputSurface> LayerTreeTest::CreateOutputSurface(bool fallback) {
   }
   output_surface_ = output_surface.get();
 
-  if (settings_.begin_frame_scheduling_enabled &&
-      settings_.throttle_frame_production) {
+  if (settings_.begin_frame_receiver && settings_.throttle_frame_production) {
     DCHECK(external_begin_frame_source_);
     DCHECK(external_begin_frame_source_->is_ready());
   }