autofill: render autofill ui in fullscreen for tv

When IME and autofill are both showing on TV, it's confusing which
window has the input focus. This CL changes autofill window to
full screen for TV.

Bug: 72122929
Test: Manual tested on TV with github example. Manually tested on
phone that UI doesn't change.

Change-Id: Id97b6389523b2ee744d02f5bc7847b307b0b29e4