cc: Move copy requests from layers to the effect tree

cc/layers/layer.h

Index: cc/layers/layer.h
diff --git a/cc/layers/layer.h b/cc/layers/layer.h
index 78cf2fa10ba10ee13a9689ba35682302b8d6f62e..c56ff2998d920c18605c3655be549ae6450d3cf4 100644
--- a/cc/layers/layer.h
+++ b/cc/layers/layer.h
@@ -106,6 +106,9 @@ class CC_EXPORT Layer : public base::RefCounted<Layer> {
     return !copy_requests_.empty();
   }
 
+  void TakeCopyRequests(
+      std::vector<std::unique_ptr<CopyOutputRequest>>* requests);
+
   virtual void SetBackgroundColor(SkColor background_color);
   SkColor background_color() const { return background_color_; }
   void SetSafeOpaqueBackgroundColor(SkColor background_color);