Extract and dispatch device uuid in media device attached notification message.

chrome/browser/media_gallery/media_device_notifications_chromeos.h

Index: chrome/browser/media_gallery/media_device_notifications_chromeos.h
diff --git a/chrome/browser/media_gallery/media_device_notifications_chromeos.h b/chrome/browser/media_gallery/media_device_notifications_chromeos.h
index cf00cf18711fac73bd76bf4f4b6fe3e083e2c70c..8b73abc6f330137a921135bc920b18ba1ffd1904 100644
--- a/chrome/browser/media_gallery/media_device_notifications_chromeos.h
+++ b/chrome/browser/media_gallery/media_device_notifications_chromeos.h
@@ -57,11 +57,6 @@ class MediaDeviceNotifications
   void AddMountedPathOnUIThread(
       const disks::DiskMountManager::MountPointInfo& mount_info);
 
-  // The lowest available device id number.
-  // Only accessed on the UI thread.
-  // TODO(thestig) Remove this and use a device UUID instead.
-  int current_device_id_;
-
   // Mapping of relevant mount points and their corresponding mount devices.
   // Only accessed on the UI thread.
   MountMap mount_map_;