Refactoring the way begin frame sources inside scheduler work.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index f7e5bf6a368b93a47f257483afe58d5b78e99933..0282e1981fccf1cffe6424feb253692dd5518e72 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -234,6 +234,7 @@ LayerTreeHostImpl::LayerTreeHostImpl(
     int id)
     : client_(client),
       proxy_(proxy),
+      needs_begin_frames_(false),
       use_gpu_rasterization_(false),
       input_handler_client_(NULL),
       did_lock_scrolling_layer_(false),
@@ -1432,7 +1433,7 @@ void LayerTreeHostImpl::SetNeedsRedrawRect(const gfx::Rect& damage_rect) {
 }
 
 void LayerTreeHostImpl::BeginFrame(const BeginFrameArgs& args) {
-  client_->BeginFrame(args);
+  CallOnBeginFrame(args);
 }
 
 void LayerTreeHostImpl::DidSwapBuffers() {
@@ -1672,7 +1673,12 @@ bool LayerTreeHostImpl::SwapBuffers(const LayerTreeHostImpl::FrameData& frame) {
   return true;
 }
 
-void LayerTreeHostImpl::SetNeedsBeginFrame(bool enable) {
+bool LayerTreeHostImpl::NeedsBeginFrames() const {
+  return needs_begin_frames_;
+}
+
+void LayerTreeHostImpl::SetNeedsBeginFrames(bool enable) {
+  needs_begin_frames_ = enable;
   if (output_surface_)
     output_surface_->SetNeedsBeginFrame(enable);
   else
@@ -3153,6 +3159,10 @@ BeginFrameArgs LayerTreeHostImpl::CurrentBeginFrameArgs() const {
                                 BeginFrameArgs::DefaultInterval());
 }
 
+void LayerTreeHostImpl::AsValueInto(base::debug::TracedValue* value) const {
+  return AsValueWithFrameInto(NULL, value);
+}
+
 scoped_refptr<base::debug::ConvertableToTraceFormat>
 LayerTreeHostImpl::AsValue() const {
   return AsValueWithFrame(NULL);