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 aa7c5a2c1f309bd8df19eb629d9b233696c39c65..0e338b06953603619fd0659f3e7003d7572688b1 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -225,7 +225,8 @@ LayerTreeHostImpl::LayerTreeHostImpl(
     RenderingStatsInstrumentation* rendering_stats_instrumentation,
     SharedBitmapManager* manager,
     int id)
-    : client_(client),
+    : BeginFrameSourceMixIn(),
+      client_(client),
       proxy_(proxy),
       use_gpu_rasterization_(false),
       input_handler_client_(NULL),
@@ -1433,7 +1434,7 @@ void LayerTreeHostImpl::SetNeedsRedrawRect(const gfx::Rect& damage_rect) {
 }
 
 void LayerTreeHostImpl::BeginFrame(const BeginFrameArgs& args) {
-  client_->BeginFrame(args);
+  CallOnBeginFrame(args);
 }
 
 void LayerTreeHostImpl::DidSwapBuffers() {
@@ -1673,7 +1674,7 @@ bool LayerTreeHostImpl::SwapBuffers(const LayerTreeHostImpl::FrameData& frame) {
   return true;
 }
 
-void LayerTreeHostImpl::SetNeedsBeginFrame(bool enable) {
+void LayerTreeHostImpl::OnNeedsBeginFramesChange(bool enable) {
   if (output_surface_)
     output_surface_->SetNeedsBeginFrame(enable);
   else
@@ -3169,6 +3170,10 @@ 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);