mono/MonoGame — pull request #2713 by danzel (2014-06-14 09:28:59+00:00)
Title: Add Obscured/Unobscured listeners 

So we know when popups are in front of us.
We set IsActive=false while a popup is obscuring us, as per WP7 behavior:
http://msdn.microsoft.com/en-us/library/microsoft.xna.framework.game.isactive.aspx

Fixes #2709