Activate LayerImpl tree with sync+push instead of pointer swap

cc/delegated_renderer_layer_impl.cc

Index: cc/delegated_renderer_layer_impl.cc
diff --git a/cc/delegated_renderer_layer_impl.cc b/cc/delegated_renderer_layer_impl.cc
index 3c7734f1071e1724ccd51b8045fe8c9c221cd791..483a256fc96831e60cbd868a24763e7b0b0b6e81 100644
--- a/cc/delegated_renderer_layer_impl.cc
+++ b/cc/delegated_renderer_layer_impl.cc
@@ -60,6 +60,11 @@ void DelegatedRendererLayerImpl::ClearRenderPasses() {
   render_passes_in_draw_order_.clear();
 }
 
+scoped_ptr<LayerImpl> DelegatedRendererLayerImpl::createLayerImpl(LayerTreeImpl* treeImpl)
+{
+    return DelegatedRendererLayerImpl::create(treeImpl, id()).PassAs<LayerImpl>();
+}
+
 void DelegatedRendererLayerImpl::didLoseOutputSurface() {
   ClearRenderPasses();
 }