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

src/gpu/GrImmediateDrawTarget.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrImmediateDrawTarget_DEFINED
 #define GrImmediateDrawTarget_DEFINED
 
@@ skipping 19 matching lines @@
                           bool insideClip,
                           GrRenderTarget* renderTarget) override;
 
     void discard(GrRenderTarget*) override;
 
 private:
     void onReset() override;
     void onFlush() override;
 
     // overrides from GrDrawTarget
-    void onDrawBatch(GrBatch*) override;
+    void onDrawBatch(GrDrawBatch*) override;
     void onStencilPath(const GrPipelineBuilder&,
                        const GrPathProcessor*,
                        const GrPath*,
                        const GrScissorState&,
                        const GrStencilSettings&) override {
         SkFAIL("Only batch implemented\n");
     }
     void onDrawPath(const GrPathProcessor*,
                     const GrPath*,
                     const GrStencilSettings&,
@@ skipping 21 matching lines @@
 
     bool isIssued(uint32_t drawID) override { return drawID != fDrawID; }
 
     GrBatchTarget fBatchTarget;
     uint32_t fDrawID;
 
     typedef GrClipTarget INHERITED;
 };
 
 #endif