LayoutLib: Stub AM/PM keycodes in Time Picker.

TimePickerSpinnerDelegate doesn't need to deal with input when running
inside LayoutLib. So, we just return the keycodes as if it's running in
English locale.

Bug: http://b.android.com/79189
Change-Id: Ife0ae91a1e34a8dac379bc1dda1c1c8ed461c164