Add ShareGroup stub

gpu/command_buffer/client/ref_counted.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef GPU_COMMAND_BUFFER_CLIENT_REF_COUNTED_H_
+#define GPU_COMMAND_BUFFER_CLIENT_REF_COUNTED_H_
+
+#if defined(__native_client__)
+#include "native_client/src/include/ref_counted.h"
+namespace gpu {
+template <class T>
+struct RefCountedThreadSafe : public nacl::RefCounted<T> {
+};
+}
+#else
+#include "base/memory/ref_counted.h"
+namespace gpu {
+template <class T>
+struct RefCountedThreadSafe : public base::RefCountedThreadSafe<T> {
+};
+}
+#endif
+
+#endif  // GPU_COMMAND_BUFFER_CLIENT_REF_COUNTED_H_