Add option to draw wireframe batch bounds

src/gpu/batches/GrCopySurfaceBatch.h

Index: src/gpu/batches/GrCopySurfaceBatch.h
diff --git a/src/gpu/batches/GrCopySurfaceBatch.h b/src/gpu/batches/GrCopySurfaceBatch.h
index ed5e77f5b061d9bce393c3a30f4f2f3eeffe410a..7bf8d8d8c271645a21dfcd16a50f898a687f55c5 100644
--- a/src/gpu/batches/GrCopySurfaceBatch.h
+++ b/src/gpu/batches/GrCopySurfaceBatch.h
@@ -26,6 +26,7 @@ public:
         GrRenderTarget* rt = fDst.get()->asRenderTarget();
         return rt ? rt->getUniqueID() : 0;
     }
+    GrRenderTarget* renderTarget() const override { return fDst.get()->asRenderTarget(); }
 
     SkString dumpInfo() const override {
         SkString string;