lib: Use the best available video format
lib: Use the best available video format

For videosites.

https://bugzilla.gnome.org/show_bug.cgi?id=673209

MathieuDuponchelle/totem-pl-parser,pwithnall/totem-pl-parser,pwithnall/totem-pl-parser,MathieuDuponchelle/totem-pl-parser,MathieuDuponchelle/totem-pl-parser,MathieuDuponchelle/totem-pl-parser