Add GpuCommandBuffer support.

src/gpu/vk/GrVkGpuCommandBuffer.h

+/*
+* Copyright 2016 Google Inc.
+*
+* Use of this source code is governed by a BSD-style license that can be
+* found in the LICENSE file.
+*/
+
+#ifndef GrVkGpuCommandBuffer_DEFINED
+#define GrVkGpuCommandBuffer_DEFINED
+
+#include "GrGpuCommandBuffer.h"
+
+#include "GrColor.h"
+
+class GrVkGpu;
+class GrVkRenderPass;
+class GrVkRenderTarget;
+class GrVkSecondaryCommandBuffer;
+
+class GrVkGpuCommandBuffer : public GrGpuCommandBuffer {
+public:
+    GrVkGpuCommandBuffer(GrVkGpu* gpu,
+                         const GrVkRenderTarget&,
+                         LoadAndStoreOp colorOp, GrColor colorClear,
+                         LoadAndStoreOp stencilOp, GrColor stencilClear);
+
+    virtual ~GrVkGpuCommandBuffer();
+
+    void end() override;
+
+    void submit() override;
+
+private:
+    const GrVkRenderPass*       fRenderPass;
+    GrVkSecondaryCommandBuffer* fCommandBuffer;
+    GrVkGpu*                    fGpu;
+
+    typedef GrGpuCommandBuffer INHERITED;
+};
+
+#endif