Split GrDrawBatch and GrVertexBatch into their own files

src/gpu/batches/GrVertexBatch.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 GrVertexBatch_DEFINED
+#define GrVertexBatch_DEFINED
+
+#include "GrDrawBatch.h"
+#include "GrBatchTarget.h"
+
+/**
+ * Base class for vertex-based GrBatches.
+ */
+class GrVertexBatch : public GrDrawBatch {
+public:
+    GrVertexBatch();
+
+    virtual void generateGeometry(GrBatchTarget*) = 0;
+
+    // TODO this goes away when batches are everywhere
+    void setNumberOfDraws(int numberOfDraws) { fNumberOfDraws = numberOfDraws; }
+    int numberOfDraws() const { return fNumberOfDraws; }
+
+protected:
+    /** Helper for rendering instances using an instanced index index buffer. This class creates the
+        space for the vertices and flushes the draws to the batch target. */
+   class InstancedHelper {
+   public:
+        InstancedHelper() {}
+        /** Returns the allocated storage for the vertices. The caller should populate the before
+            vertices before calling issueDraws(). */
+        void* init(GrBatchTarget* batchTarget, GrPrimitiveType, size_t vertexStride,
+                   const GrIndexBuffer*, int verticesPerInstance, int indicesPerInstance,
+                   int instancesToDraw);
+
+        /** Call after init() to issue draws to the batch target.*/
+        void issueDraw(GrBatchTarget* batchTarget) {
+            SkASSERT(fVertices.instanceCount());
+            batchTarget->draw(fVertices);
+        }
+    private:
+        GrVertices  fVertices;
+    };
+
+    static const int kVerticesPerQuad = 4;
+    static const int kIndicesPerQuad = 6;
+
+    /** A specialization of InstanceHelper for quad rendering. */
+    class QuadHelper : private InstancedHelper {
+    public:
+        QuadHelper() : INHERITED() {}
+        /** Finds the cached quad index buffer and reserves vertex space. Returns NULL on failure
+            and on sucess a pointer to the vertex data that the caller should populate before
+            calling issueDraws(). */
+        void* init(GrBatchTarget* batchTarget, size_t vertexStride, int quadsToDraw);
+
+        using InstancedHelper::issueDraw;
+
+    private:
+        typedef InstancedHelper INHERITED;
+    };
+
+private:
+    int                                 fNumberOfDraws;
+    typedef GrDrawBatch INHERITED;
+};
+
+#endif