compositor-worker: Initialize CW machinery plumbing to compositor and fire CW rAF callbacks.

cc/trees/remote_channel_impl.h

Index: cc/trees/remote_channel_impl.h
diff --git a/cc/trees/remote_channel_impl.h b/cc/trees/remote_channel_impl.h
index 122e790b39a8ff5ccdc62331c36cc924611a9c28..dac3653a936c964e1ec7b7dd204e1b11234f0cce 100644
--- a/cc/trees/remote_channel_impl.h
+++ b/cc/trees/remote_channel_impl.h
@@ -158,6 +158,7 @@ class CC_EXPORT RemoteChannelImpl : public ChannelImpl,
   void Start(
       std::unique_ptr<BeginFrameSource> external_begin_frame_source) override;
   void Stop() override;
+  void SetMutator(LayerTreeMutator* mutator) override;
   bool SupportsImplScrolling() const override;
   void SetChildrenNeedBeginFrames(bool children_need_begin_frames) override;
   void SetAuthoritativeVSyncInterval(const base::TimeDelta& interval) override;