Iterate over instanced draws in GrGpu rather than above GrBatchTarget

src/gpu/GrRectBatch.cpp

Index: src/gpu/GrRectBatch.cpp
diff --git a/src/gpu/GrRectBatch.cpp b/src/gpu/GrRectBatch.cpp
index ba63db1e0f38649d41058906fca1a17db2a95665..ab9ce4febcb3f1eb0ee550cfe3f67b087ec3e0fb 100644
--- a/src/gpu/GrRectBatch.cpp
+++ b/src/gpu/GrRectBatch.cpp
@@ -156,7 +156,7 @@ public:
             }
         }
 
-        helper.issueDraws(batchTarget);
+        helper.issueDraw(batchTarget);
     }
 
     SkSTArray<1, Geometry, true>* geoData() { return &fGeoData; }