Add GpuCommandBuffer support.

src/gpu/gl/GrGLGpuCommandBuffer.h

Index: src/gpu/gl/GrGLGpuCommandBuffer.h
diff --git a/src/gpu/gl/GrGLGpuCommandBuffer.h b/src/gpu/gl/GrGLGpuCommandBuffer.h
new file mode 100644
index 0000000000000000000000000000000000000000..8925322d4a3decb0384f84b6811886d4fa8661de
--- /dev/null
+++ b/src/gpu/gl/GrGLGpuCommandBuffer.h
@@ -0,0 +1,33 @@
+/*
+* 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 GrGLGpuCommandBuffer_DEFINED
+#define GrGLGpuCommandBuffer_DEFINED
+
+#include "GrGpuCommandBuffer.h"
+
+class GrGLGpu;
+
+class GrGLGpuCommandBuffer : public GrGpuCommandBuffer {
+public:
+    GrGLGpuCommandBuffer(GrGLGpu* gpu) /*: fGpu(gpu)*/ {}
+
+    virtual ~GrGLGpuCommandBuffer() {}
+
+    void end() override {}
+
+    void submit() override {}
+
+private:
+    // commented out to appease clang compiler warning about unused private field
+   // GrGLGpu*                    fGpu;
+
+    typedef GrGpuCommandBuffer INHERITED;
+};
+
+#endif
+