Remove NfcFragment from activity when no longer sharing.

This fixes scenarios where the same activity sets, unsets
and re-sets an NdefMessage and/or callback.

Bug: 5454848
Change-Id: I5ed98047b9cfe90d2f48656d978f2d08bb4bf0cc

Author: Martijn Coenen

core/java/android/nfc/NfcActivityManager.java

@@ -162,6 +162,7 @@ synchronized NfcActivityState getOrCreateState(Activity activity, boolean create
     synchronized void maybeRemoveState(Activity activity, NfcActivityState state) {
         if (state.ndefMessage == null && state.ndefMessageCallback == null &&
                 state.onNdefPushCompleteCallback == null) {
+            NfcFragment.remove(activity);
             mNfcState.remove(activity);
         }
     }