Remove screenshot window focus on touch outside.

Reimplementing workound from R, needed some significant changes because
of insets work in S.

Bug: 186397778
Test: Take a screenshot, tap an input box, observe IME come up.
Test: Take a screenshot, swipe back, obseve screenshot UI closes.
Test: Validate all screenshot buttons are tappable and swipable.
Change-Id: Icec465337f441f4dcd0addd0459c5ccd238935a5