cc: Merge the DrawLayer()/DrawFrame() and SwapBuffers() methods.

cc/trees/single_thread_proxy.cc

Index: cc/trees/single_thread_proxy.cc
diff --git a/cc/trees/single_thread_proxy.cc b/cc/trees/single_thread_proxy.cc
index 4ce74a6dd718ca51ca6e736e81e05153d649dcce..429845b5343acb4c57100e29ca3d29c1b4d57b67 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -573,8 +573,7 @@ DrawResult SingleThreadProxy::DoComposite(LayerTreeHostImpl::FrameData* frame) {
     draw_result = layer_tree_host_impl_->PrepareToDraw(frame);
     draw_frame = draw_result == DRAW_SUCCESS;
     if (draw_frame) {
-      layer_tree_host_impl_->DrawLayers(frame);
-      if (layer_tree_host_impl_->SwapBuffers(*frame)) {
+      if (layer_tree_host_impl_->DrawLayers(frame)) {
         if (scheduler_on_impl_thread_)
           scheduler_on_impl_thread_->DidSwapBuffers();
         client_->DidPostSwapBuffers();