Use factory method to create VideoCaptureDeviceFactory .

media/video/capture/video_capture_device_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 MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_FACTORY_H_
 #define MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_FACTORY_H_
 
 #include "base/threading/thread_checker.h"
 #include "media/video/capture/video_capture_device.h"
 
@@ skipping 35 matching lines @@
       ImageCaptureFormats* supported_formats) {}
 
  protected:
   // Gets the names of all video capture devices connected to this computer.
   // Used by the default implementation of EnumerateDeviceNames().
   virtual void GetDeviceNames(VideoCaptureDevice::Names* device_names) = 0;
 
   base::ThreadChecker thread_checker_;
 
  private:
+  static VideoCaptureDeviceFactory* CreateVideoCaptureDeviceFactory(
+      scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner);
+
   DISALLOW_COPY_AND_ASSIGN(VideoCaptureDeviceFactory);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_FACTORY_H_