Introduce GrBatch subclasses GrDrawBatch and GrVertexBatch to prepare for non-drawing batches

src/gpu/batches/GrStrokeRectBatch.h

Index: src/gpu/batches/GrStrokeRectBatch.h
diff --git a/src/gpu/batches/GrStrokeRectBatch.h b/src/gpu/batches/GrStrokeRectBatch.h
index 7979a6492d856ae5bee0e774520da8eee421f8a0..2c891a467d2412f552673c5191e835cefa55dafe 100644
--- a/src/gpu/batches/GrStrokeRectBatch.h
+++ b/src/gpu/batches/GrStrokeRectBatch.h
@@ -12,7 +12,7 @@
 #include "GrColor.h"
 #include "GrDefaultGeoProcFactory.h"
 
-class GrStrokeRectBatch : public GrBatch {
+class GrStrokeRectBatch : public GrVertexBatch {
 public:
     struct Geometry {
         GrColor fColor;
@@ -21,7 +21,7 @@ public:
         SkScalar fStrokeWidth;
     };
 
-    static GrBatch* Create(const Geometry& geometry, bool snapToPixelCenters) {
+    static GrDrawBatch* Create(const Geometry& geometry, bool snapToPixelCenters) {
         return SkNEW_ARGS(GrStrokeRectBatch, (geometry, snapToPixelCenters));
     }