compositor-worker: cc->blink mutation plumbing

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 8b1227270b5f39e3cfefa936052e0f585d6c55e0..2a672f15ac3e72d7feda1d17c6f07bfd5e1c8ec8 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -15,6 +15,7 @@
 #include <utility>
 
 #include "base/auto_reset.h"
+#include "base/bind.h"
 #include "base/containers/small_map.h"
 #include "base/json/json_writer.h"
 #include "base/metrics/histogram.h"
@@ -25,6 +26,7 @@
 #include "cc/animation/animation_events.h"
 #include "cc/animation/animation_host.h"
 #include "cc/animation/animation_id_provider.h"
+#include "cc/animation/layer_tree_mutations_callback.h"
 #include "cc/animation/scroll_offset_animation_curve.h"
 #include "cc/animation/timing_function.h"
 #include "cc/base/histograms.h"
@@ -3253,6 +3255,14 @@ void LayerTreeHostImpl::PinchGestureEnd() {
   SetNeedsRedraw();
 }
 
+scoped_ptr<BeginFrameCallbackList>
+LayerTreeHostImpl::ProcessLayerTreeMutations() {
+  // TODO(majidvp): This is where we turn |LayerTreeMutationsCallback| into
+  // a list of closures.
+  auto callbacks = make_scoped_ptr(new BeginFrameCallbackList());
+  return callbacks;
+}
+
 static void CollectScrollDeltas(ScrollAndScaleSet* scroll_info,
                                 LayerImpl* layer_impl) {
   if (!layer_impl)