compositor-worker: cc->blink mutation plumbing

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index 5222b41d956139a64fb231d456bc22ff0d261f54..5e4682456af4fa138e2b7812d7a4ae20813c9a4a 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -298,6 +298,7 @@ class COMPOSITOR_EXPORT Compositor
                            const gfx::Vector2dF& elastic_overscroll_delta,
                            float page_scale,
                            float top_controls_delta) override {}
+  void ApplyMutations(const cc::LayerTreeMutations& mutations) override {}
   void RequestNewOutputSurface() override;
   void DidInitializeOutputSurface() override;
   void DidFailToInitializeOutputSurface() override;