Add getTitle() for ButtonPreference

Bug: 233038449
Test: make RunSettingsRoboTests ROBOTEST_FILTER=ButtonPreferenceTest
Change-Id: Ie2f24879bce026e5bc3d7fedfcb3a6475ab7d404
Merged-In: Ie2f24879bce026e5bc3d7fedfcb3a6475ab7d404
2 files changed