Update the bouncer to be able to move to either side of a wide screen.

I'd like to test other things (like tap makes the IME move), but to do
that means replacing the mock with a proper fake. That can come later,
but this at least tests that the flagging works correctly.

The changes between this and
commit cae34b8e is the bouncer height is
now measured using wrap_content, so the placement can be controlled
properly by the outer View (as the position of the bouncer changes
depending on the size of the screen).

This reverts commit cae34b8e.

Test: Included
Bug: 170858298
Change-Id: I18428a6df9abf0e8e37c1c179be6843e4eee793c