resolve merge conflicts of 2c535e27 to nyc-dev-plus-aosp

am: 51be13aa  -s ours

* commit '51be13aa':
  Add android.support.design proguard flags
  Use ACTION_LOCKED_BOOT_COMPLETED on API 24+ - DO NOT MERGE
  Teach DeskClock about file-based encryption. - DO NOT MERGE
  Refactoring SharedPreferences to common location. - DO NOT MERGE
  Use AppCompat's imageButtonStyle attribute - DO NOT MERGE
  Use SimpleItemAnimator - DO NOT MERGE
  Bump version to 4.5.0 - DO NOT MERGE
  Do not assume current stopwatch lap has positive duration
  Avoid IndexOutOfBounds when deleting timer - DO NOT MERGE