Add ResizingTextView to leanback library.

ResizingTextView is a class that adjusts text size automatically in response
to certain trigger conditions, such as text that wraps over multiple lines.

For now this class is only used in DetailsFragment, and is hidden from
javadocs. The API will be revisited before making it public.

Bug: 18117832
Change-Id: Ic8679e370acb48f8dcda6c1e05b23229e8f5739f
5 files changed