Gallery2: Remove slideshow option if all files of the folder are video

Enter Gallery and open folder whose files are all video, press
menu key should no slideshow option.

Add condition to remove slideshow if the folder are all video
files.

CRs-Fixed: 574984

Change-Id: Ib1603f1609b6490e44039ab64abefb44f14bd477
Gallery2: fix cropview shows abnormal if lock and rotate screen

The canvas value will effect the screenbounds value.
When screen is locked, the screen orientation will be force
changed to portrait but the screenbounds will still use
landscape value.

To fix this issue, if found screenbounds changed, we will make
dirty true to update the view.

CRs-Fixed: 557210

Change-Id: Ia84581d122da76f084117dfd0a195ce2784e18c9