Move prepareForExternalIO from GrRenderTarget to GrDrawContext

include/gpu/GrSurface.h

Index: include/gpu/GrSurface.h
diff --git a/include/gpu/GrSurface.h b/include/gpu/GrSurface.h
index 8e8eb0f7e6f8eff42b041febbbdd904537f6cd3a..e002765590927ed45b1a29948e2b4209c9a7b102 100644
--- a/include/gpu/GrSurface.h
+++ b/include/gpu/GrSurface.h
@@ -114,13 +114,6 @@ public:
      */
     void flushWrites();
 
-
-    /**
-     * After this returns any pending surface IO will be issued to the backend 3D API and
-     * if the surface has MSAA it will be resolved.
-     */
-    void prepareForExternalIO();
-
     /** Access methods that are only to be used within Skia code. */
     inline GrSurfacePriv surfacePriv();
     inline const GrSurfacePriv surfacePriv() const;