Add option to draw wireframe batch bounds

src/gpu/batches/GrBatch.h

Index: src/gpu/batches/GrBatch.h
diff --git a/src/gpu/batches/GrBatch.h b/src/gpu/batches/GrBatch.h
index 03e396a29c2fd31d33753c7631f514aaac7cd4a5..a66d6ae308d6e84e84ce0efc38508f28fa867a26 100644
--- a/src/gpu/batches/GrBatch.h
+++ b/src/gpu/batches/GrBatch.h
@@ -16,6 +16,7 @@
 
 class GrCaps;
 class GrBatchFlushState;
+class GrRenderTarget;
 
 /**
  * GrBatch is the base class for all Ganesh deferred geometry generators.  To facilitate
@@ -113,6 +114,9 @@ public:
     /** Used for spewing information about batches when debugging. */
     virtual SkString dumpInfo() const = 0;
 
+    /** Can remove this when multi-draw-buffer lands */
+    virtual GrRenderTarget* renderTarget() const = 0;
+
 protected:
     // NOTE, compute some bounds, even if extremely conservative.  Do *NOT* setLargest on the bounds
     // rect because we outset it for dst copy textures