Not include fullscreen opaque window on screenshot

Extend the fullscreen meaning by adding opaque drawn check on
screenshot application; if there is a fullscreen window but not
opaque, we will continue finding behind windows; otherwise ending up
including behind windows. It's able to help avoiding capturing BLACK
screenshot bitmap.

Change-Id: I1c7e8f513c366688ea8001c3d0c799f3522f0ffd
Signed-off-by: tingna_sung <tingna_sung@htc.com>