VideoCaptureDeviceFactory: Change device enumeration to callback + QTKit enumerates in UI thread.

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"
 
 namespace media {
 
 // VideoCaptureDeviceFactory is the base class for creation of video capture
 // devices in the different platforms. VCDFs are created by MediaStreamManager
 // on IO thread and plugged into VideoCaptureManager, who owns and operates them
 // in Device Thread (a.k.a. Audio Thread).
 class MEDIA_EXPORT VideoCaptureDeviceFactory {
  public:
-  static scoped_ptr<VideoCaptureDeviceFactory> CreateFactory();
+  static scoped_ptr<VideoCaptureDeviceFactory> CreateFactory(
+      scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner);
 
   VideoCaptureDeviceFactory();
   virtual ~VideoCaptureDeviceFactory();
 
   // Creates a VideoCaptureDevice object. Returns NULL if something goes wrong.
   virtual scoped_ptr<VideoCaptureDevice> Create(
-      scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner,
-      const VideoCaptureDevice::Name& device_name);
+      const VideoCaptureDevice::Name& device_name) = 0;
 
-  // Gets the names of all video capture devices connected to this computer.
-  virtual void GetDeviceNames(VideoCaptureDevice::Names* device_names);
+  // Asynchronous version of GetDeviceNames calling back to |callback|.
+  virtual void EnumerateDeviceNames(const base::Callback<
+      void(scoped_ptr<media::VideoCaptureDevice::Names>)>& callback);
 
   // Gets the supported formats of a particular device attached to the system.
   // This method should be called before allocating or starting a device. In
   // case format enumeration is not supported, or there was a problem, the
   // formats array will be empty.
   virtual void GetDeviceSupportedFormats(
       const VideoCaptureDevice::Name& device,
-      VideoCaptureFormats* supported_formats);
+      VideoCaptureFormats* supported_formats) = 0;
 
  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:
   DISALLOW_COPY_AND_ASSIGN(VideoCaptureDeviceFactory);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_FACTORY_H_