Use factory method to create VideoCaptureDeviceFactory .

media/video/capture/mac/video_capture_device_factory_mac.mm

 // 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.
 
 #include "media/video/capture/mac/video_capture_device_factory_mac.h"
 
 #import <IOKit/audio/IOAudioTypes.h>
 
 #include "base/bind.h"
 #include "base/location.h"
@@ skipping 186 matching lines @@
   case VideoCaptureDevice::Name::DECKLINK:
     DVLOG(1) << "Enumerating video capture capabilities " << device.name();
     VideoCaptureDeviceDeckLinkMac::EnumerateDeviceCapabilities(
         device, supported_formats);
     break;
   default:
     NOTREACHED();
   }
 }
 
+// static
+VideoCaptureDeviceFactory*
+VideoCaptureDeviceFactory::CreateVideoCaptureDeviceFactory(
+    scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner) {
+  return new VideoCaptureDeviceFactoryMac(ui_task_runner);
+}
+
 }  // namespace media