Hide the increased window size due to colored bars from the view hierarchy

For windows with L-bars, the window size has been extended
to include the area below the nav bar. This change makes
DecorView hide that fact from the rest of the view hierarchy,
unless it has explicitly ask to extend below the navigation bar.

Bug: 17421744
Change-Id: I7bd32531130d199c0734ffcb800194e77b7e16c3