Add ability of setting content description for footer

Test: Rebuilt lib and confirmed to set a content description for a footer
in Settings app. Then, talkback can say correct description.
Fix: 188009297
Change-Id: I7af451a553a13d5108ab279d149e4cdfdfcb620f

Change-Id: I06c5fbdfca25e287988ea8ef8eca56fcce10857a
2 files changed