Add getSessionName() API for group name in worker

Bug: 150827723
Test: make -j50 RunSettingsRoboTests
Change-Id: Id09cb61b8ce23520761252fbb8ffbe3e323adf8e

src/com/android/settings/media/MediaDeviceUpdateWorker.java

@@ -174,6 +174,10 @@ public class MediaDeviceUpdateWorker extends SliceBackgroundWorker
         return mLocalMediaManager.getSessionVolume();
     }
 
+    CharSequence getSessionName() {
+        return mLocalMediaManager.getSessionName();
+    }
+
     /**
      * Find the active MediaDevice.
      *