WIP - compositor worker mega patch.

cc/trees/proxy_impl.cc

Index: cc/trees/proxy_impl.cc
diff --git a/cc/trees/proxy_impl.cc b/cc/trees/proxy_impl.cc
index f9a1eab474149707070f992ef62d1be392b60d2b..dea6ce1b67c527bbb0a9cd563483abaf87cdff07 100644
--- a/cc/trees/proxy_impl.cc
+++ b/cc/trees/proxy_impl.cc
@@ -111,6 +111,12 @@ void ProxyImpl::SetThrottleFrameProductionOnImpl(bool throttle) {
   scheduler_->SetThrottleFrameProduction(throttle);
 }
 
+void ProxyImpl::InitializeMutatorOnImpl(LayerTreeMutator* mutator) {
+  TRACE_EVENT0("cc,compositor-worker", "ProxyImpl::InitializeMutatorOnImpl");
+  DCHECK(IsImplThread());
+  layer_tree_host_impl_->SetLayerTreeMutator(mutator);
+}
+
 void ProxyImpl::UpdateTopControlsStateOnImpl(TopControlsState constraints,
                                              TopControlsState current,
                                              bool animate) {
@@ -501,6 +507,9 @@ void ProxyImpl::ScheduledActionSendBeginMainFrame(const BeginFrameArgs& args) {
   begin_main_frame_state->begin_frame_args = args;
   begin_main_frame_state->scroll_info =
       layer_tree_host_impl_->ProcessScrollDeltas();
+  if (LayerTreeMutator* mutator = layer_tree_host_impl_->mutator())
+    begin_main_frame_state->mutations = mutator->TakeMutations();
+
   begin_main_frame_state->memory_allocation_limit_bytes =
       layer_tree_host_impl_->memory_allocation_limit_bytes();
   begin_main_frame_state->evicted_ui_resources =