Add target fragment for RoamingDialogFragment

Bug: 114749736
Test: Manual
Change-Id: I6f2939d99b72ff2dcf094c84bac75c2ca5d7ff66

src/com/android/settings/mobilenetwork/MobileNetworkFragment.java

@@ -1074,6 +1074,7 @@ public class MobileNetworkFragment extends DashboardFragment implements
                     Bundle b = new Bundle();
                     b.putInt(RoamingDialogFragment.SUB_ID_KEY, mSubId);
                     fragment.setArguments(b);
+                    fragment.setTargetFragment(this, 0 /* requestCode */);
                     fragment.show(getFragmentManager(), ROAMING_TAG);
                     // Don't update the toggle unless the confirm button is actually pressed.
                     return false;

src/com/android/settings/mobilenetwork/RoamingDialogFragment.java

@@ -60,7 +60,6 @@ public class RoamingDialogFragment extends InstrumentedDialogFragment implements
         mSubId = args.getInt(SUB_ID_KEY);
         mCarrierConfigManager = new CarrierConfigManager(context);
 
-        //TODO(b/114749736): set target fragment in host fragment
         Fragment fragment = getTargetFragment();
         try {
             mListener = (RoamingDialogListener) fragment;