added gpu_benchmarking_extension boilerplate and hooked it up to a new switch.

content/renderer/gpu/gpu_benchmarking_extension.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 CONTENT_RENDERER_GPU_GPU_BENCHMARKING_EXTENSION_H_
+#define CONTENT_RENDERER_GPU_GPU_BENCHMARKING_EXTENSION_H_
+#pragma once
+
+namespace v8 {
+class Extension;
+}
+
+namespace content {
+
+// V8 extension for gpu benchmarking
+class GpuBenchmarkingExtension {
+ public:
+  static v8::Extension* Get();
+};
+
+}  // namespace content
+
+#endif // CONTENT_RENDERER_GPU_GPU_BENCHMARKING_EXTENSION_H_