gpu: Have GpuService create and own GpuMemoryBufferFactory.

gpu/ipc/service/gpu_memory_buffer_factory.h

 // Copyright 2014 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_IPC_SERVICE_GPU_MEMORY_BUFFER_FACTORY_H_
 #define GPU_IPC_SERVICE_GPU_MEMORY_BUFFER_FACTORY_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "gpu/gpu_export.h"
 #include "gpu/ipc/common/surface_handle.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/gpu_memory_buffer.h"
 
 namespace gpu {
 
 class ImageFactory;
 
 class GPU_EXPORT GpuMemoryBufferFactory {
  public:
   virtual ~GpuMemoryBufferFactory() {}
 
-  // Creates a new factory instance for native GPU memory buffers.
+  // Creates a new factory instance for native GPU memory buffers. Returns null
+  // if native buffers are not supported.
   static std::unique_ptr<GpuMemoryBufferFactory> CreateNativeType();
 
   // Creates a new GPU memory buffer instance. A valid handle is returned on
   // success. It can be called on any thread.
   virtual gfx::GpuMemoryBufferHandle CreateGpuMemoryBuffer(
       gfx::GpuMemoryBufferId id,
       const gfx::Size& size,
       gfx::BufferFormat format,
       gfx::BufferUsage usage,
       int client_id,
@@ skipping 10 matching lines @@
  protected:
   GpuMemoryBufferFactory() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(GpuMemoryBufferFactory);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_IPC_SERVICE_GPU_MEMORY_BUFFER_FACTORY_H_