Sort camera device list to use front camera first

media/capture/video/linux/video_capture_device_factory_linux.cc

Index: media/capture/video/linux/video_capture_device_factory_linux.cc
diff --git a/media/capture/video/linux/video_capture_device_factory_linux.cc b/media/capture/video/linux/video_capture_device_factory_linux.cc
index 14a1ca12e6b4c5679e1ed4efd5fc3df4b9aae3a2..7b9bbf0bffc78ab9623a80908039fc3060e20d1a 100644
--- a/media/capture/video/linux/video_capture_device_factory_linux.cc
+++ b/media/capture/video/linux/video_capture_device_factory_linux.cc
@@ -228,6 +228,7 @@ void VideoCaptureDeviceFactoryLinux::GetDeviceDescriptors(
 #endif
     }
   }
+  std::sort(device_descriptors->begin(), device_descriptors->end());

[mtomasz, 2017/01/23 07:15:22]

Does it mean that the default camera in chrome://settings will be set to the
facing one (unless it's explicitly changed by user)?

[henryhsu, 2017/01/23 08:04:38]

I don't see default camera in chrome://settings.
But I believe chrome chooses the first one in the list as the default camera.
I tried to powerwash the device and changed the order of the list.
I can see the camera app used the first camera of the provided list.

[shenghao, 2017/01/23 10:18:21]

May you add comment to document the reason we want to sort it?

[henryhsu, 2017/01/23 11:25:20]

Done.

 }
 
 void VideoCaptureDeviceFactoryLinux::GetSupportedFormats(