gpu: Have GpuService create and own GpuMemoryBufferFactory.

content/browser/gpu/gpu_main_thread_factory.h

 // Copyright 2017 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_BROWSER_GPU_GPU_MAIN_THREAD_FACTORY_H_
 #define CONTENT_BROWSER_GPU_GPU_MAIN_THREAD_FACTORY_H_
 
 #include "content/common/content_export.h"
 
 namespace base {
 class Thread;
 }
 
-namespace gpu {
-struct GpuPreferences;
-}
-
 namespace content {
 class InProcessChildThreadParams;
 
 typedef base::Thread* (*GpuMainThreadFactoryFunction)(
-    const InProcessChildThreadParams&,
-    const gpu::GpuPreferences&);
+    const InProcessChildThreadParams&);
 
 CONTENT_EXPORT void RegisterGpuMainThreadFactory(
     GpuMainThreadFactoryFunction create);
 
 GpuMainThreadFactoryFunction GetGpuMainThreadFactory();
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_GPU_GPU_MAIN_THREAD_FACTORY_H_