Fix canexchange conditions
Fix canexchange conditions

Code from Daniel Stone.
Now Chromium will hit this fast path when system window decorations are
disabled, when maximized, full screen, and windowed.

Popolon/xf86-video-armsoc,commshare/xf86-video-armsoc,Popolon/xf86-video-armsoc,commshare/xf86-video-armsoc