add SkImageInfo to SkGrPixelRef constructor, to prep for larger CL

include/gpu/SkGrPixelRef.h

Index: include/gpu/SkGrPixelRef.h
diff --git a/include/gpu/SkGrPixelRef.h b/include/gpu/SkGrPixelRef.h
index da4b8fae090dfab8d0fd6860426a612a5d5de52f..c29c27fb3bdc0b3d0963fcaa0fda82ef3d0285a1 100644
--- a/include/gpu/SkGrPixelRef.h
+++ b/include/gpu/SkGrPixelRef.h
@@ -47,7 +47,8 @@ public:
      * cache and would like the pixel ref to unlock it in its destructor then transferCacheLock
      * should be set to true.
      */
-    SkGrPixelRef(GrSurface* surface, bool transferCacheLock = false);
+    SkGrPixelRef(GrSurface*, bool transferCacheLock = false);
+    SkGrPixelRef(const SkImageInfo&, GrSurface*, bool transferCacheLock = false);
     virtual ~SkGrPixelRef();
 
     // override from SkPixelRef