Fix layout for full-screen floating windows

When the app doesn't set IN_SCREEN and INSET_DECOR but the window is
still full-screen, we force SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN but then
we still need to communicate the content insets to the DecorView.

In DecorView, we consume these insets in this mode and set it as
layout params so this behavior is completely transparent for the
app.

Bug: 26464646
Change-Id: Ib7332b845767a5bbc0266c380bf6240e322db943