Spruce up batch info printouts

src/gpu/batches/GrTInstanceBatch.h

Index: src/gpu/batches/GrTInstanceBatch.h
diff --git a/src/gpu/batches/GrTInstanceBatch.h b/src/gpu/batches/GrTInstanceBatch.h
index c501fd967afb50df2282877d65415d6e95426beb..e63f2e519d6cb31dba82fb108725ac1aa95cf33d 100644
--- a/src/gpu/batches/GrTInstanceBatch.h
+++ b/src/gpu/batches/GrTInstanceBatch.h
@@ -52,6 +52,7 @@ public:
 
     SkString dumpInfo() const override {
         SkString str;
+        str.appendf("# batched: %d\n", fGeoData.count());
         for (int i = 0; i < fGeoData.count(); ++i) {
             str.append(Impl::DumpInfo(fGeoData[i], i));
         }