Add thumbnailAvailable property to WindowThumbnail
Review Request #120946 - Created Nov. 2, 2014 and submitted
|Kai Uwe Broulik|
This adds a thumbnailAvailable property which tells us whether it's actually displaying a window thumbnail or just the fallback window icon.
Tested with taskmanager both with compositing on and off and minimized window (thumbnail gone and property false), restored window (thumbnail there again and property true).