Annotated mTheme field on ContextThemeWrapper with maxTargetSdk P

Added ContextThemeWrapper#setTheme(Theme) method to programmatically
assign the theme without using a resource id

Change-Id: I043253e65a535abdf8d89d9421d2cff2b41bdb05
Fixes: 123768723
Test: Added CTS test to verify setTheme
2 files changed