Fix fatal exception in FakeBroadcastReceiver.

It seems like an exception is thrown because ArraySet is not
thread-safe.

Use a synchronized hash set for the receivers.

Fixes: 261099639
Test: atest KeyguardQuickAffordanceProviderTest
Change-Id: I39c43bb2d5dbdc6705b5dec4b362d75189c136d9
1 file changed