Adding RECEIVER_EXPORTED flag.

ACTION_CLOSE_SySTEM_DIALOG has been deprecated and will be dropped by the system in non-debug builds S+, so we want to preserve the old behavior and should mark this receiver as exported for T+.

Bug:161145287
Change-Id: I27fa0cbd971d17cb2bf7852e464c1b37d41350a8
Test: no-op

src/com/android/settings/homepage/contextualcards/ContextualCardsFragment.java

@@ -129,7 +129,7 @@ public class ContextualCardsFragment extends InstrumentedFragment implements
 
     private void registerKeyEventReceiver() {
         getActivity().registerReceiver(mKeyEventReceiver,
-                new IntentFilter(Intent.ACTION_CLOSE_SYSTEM_DIALOGS));
+                new IntentFilter(Intent.ACTION_CLOSE_SYSTEM_DIALOGS), Context.RECEIVER_EXPORTED);
     }
 
     private void unregisterKeyEventReceiver() {