Make GrVertexBatch objects hold their own draws during GrDrawTarget flush

src/gpu/batches/GrDrawAtlasBatch.h

Index: src/gpu/batches/GrDrawAtlasBatch.h
diff --git a/src/gpu/batches/GrDrawAtlasBatch.h b/src/gpu/batches/GrDrawAtlasBatch.h
index 6e353ef647af711a85f436c2a6cbe283a7369194..c7ee9f3e376a18e858ea91a8945c32fa231a609a 100644
--- a/src/gpu/batches/GrDrawAtlasBatch.h
+++ b/src/gpu/batches/GrDrawAtlasBatch.h
@@ -42,11 +42,12 @@ public:
     }
     
     void initBatchTracker(const GrPipelineOptimizations&) override;
-    void generateGeometry(GrBatchTarget* batchTarget) override;
     
     SkSTArray<1, Geometry, true>* geoData() { return &fGeoData; }
     
 private:
+    void onPrepareDraws(Target*) override;
+
     GrDrawAtlasBatch(const Geometry& geometry, const SkMatrix& viewMatrix, int spriteCount,
                      const SkRSXform* xforms, const SkRect* rects, const SkColor* colors);