[Ozone-DRI] Remove the extra helper thread and reuse the IO one

ui/ozone/platform/dri/dri_gpu_platform_support.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 UI_OZONE_PLATFORM_DRI_DRI_GPU_PLATFORM_SUPPORT_H_
 #define UI_OZONE_PLATFORM_DRI_DRI_GPU_PLATFORM_SUPPORT_H_
 
 #include "base/containers/scoped_ptr_hash_map.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "ipc/message_filter.h"
 #include "ui/gfx/native_widget_types.h"
-#include "ui/ozone/platform/dri/dri_helper_thread.h"
 #include "ui/ozone/public/gpu_platform_support.h"
 
 class SkBitmap;
 
 namespace base {
 class FilePath;
+class SingleThreadTaskRunner;
 }
 
 namespace gfx {
 class Point;
 class Rect;
 }
 
 namespace ui {
 
 class DriSurfaceFactory;
@@ skipping 40 matching lines @@
   void OnRefreshNativeDisplays();
   void OnConfigureNativeDisplay(int64_t id,
                                 const DisplayMode_Params& mode,
                                 const gfx::Point& origin);
   void OnDisableNativeDisplay(int64_t id);
   void OnTakeDisplayControl();
   void OnRelinquishDisplayControl();
   void OnAddGraphicsDevice(const base::FilePath& path);
   void OnRemoveGraphicsDevice(const base::FilePath& path);
 
-  void OnFilterAdded();
+  void SetIOTaskRunner(
+      const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
 
   IPC::Sender* sender_;                       // Not owned.
   DriWrapper* drm_;                           // Not owned.
   DriWindowDelegateManager* window_manager_;  // Not owned.
   ScreenManager* screen_manager_;             // Not owned.
 
-  DriHelperThread helper_thread_;
   scoped_ptr<NativeDisplayDelegateDri> ndd_;
   ScopedVector<GpuPlatformSupport> handlers_;
   scoped_refptr<IPC::MessageFilter> filter_;
+  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PLATFORM_DRI_DRI_GPU_PLATFORM_SUPPORT_H_