WIP - compositor worker mega patch.

cc/trees/proxy_main.h

Index: cc/trees/proxy_main.h
diff --git a/cc/trees/proxy_main.h b/cc/trees/proxy_main.h
index bb510b8569a1cf4550f4119112ec11e88a8441b1..82bd318d28bf2ae48a29e9ecd3474107a1d504ed 100644
--- a/cc/trees/proxy_main.h
+++ b/cc/trees/proxy_main.h
@@ -20,6 +20,7 @@ namespace cc {
 class BeginFrameSource;
 class ChannelMain;
 class LayerTreeHost;
+class LayerTreeMutator;
 
 // This class aggregates all interactions that the impl side of the compositor
 // needs to have with the main side.
@@ -100,6 +101,7 @@ class CC_EXPORT ProxyMain : public Proxy {
   void Start(scoped_ptr<BeginFrameSource> external_begin_frame_source) override;
   void Stop() override;
   bool SupportsImplScrolling() const override;
+  void SetMutator(LayerTreeMutator* mutator) override;
   bool MainFrameWillHappenForTesting() override;
   void SetChildrenNeedBeginFrames(bool children_need_begin_frames) override;
   void SetAuthoritativeVSyncInterval(const base::TimeDelta& interval) override;