Add option to draw wireframe batch bounds

src/gpu/batches/GrDrawBatch.h

Index: src/gpu/batches/GrDrawBatch.h
diff --git a/src/gpu/batches/GrDrawBatch.h b/src/gpu/batches/GrDrawBatch.h
index 8e738789812ce6dd54e3a357d0e3c52de8e0c39a..9401c675011649a4ddb35cbe00ac09be67c27096 100644
--- a/src/gpu/batches/GrDrawBatch.h
+++ b/src/gpu/batches/GrDrawBatch.h
@@ -63,6 +63,11 @@ public:
         return this->pipeline()->getRenderTarget()->getUniqueID();
     }
 
+    GrRenderTarget* renderTarget() const final {
+        SkASSERT(fPipelineInstalled);
+        return this->pipeline()->getRenderTarget();
+    }
+
     SkString dumpInfo() const override {
         SkString string;
         string.appendf("RT: %d\n", this->renderTargetUniqueID());