Fixing height of image in mobile media viewer

Changing a .height() to an .outerHeight().

Change-Id: Id567fbe2b3d6a5ebda0c2be4726d2edbfd2b4eb2
Fixing fatal error on Special:Uploads for mobile

Also moving userCanUpload() back to MobileContext, as my assumption
about it only being called from SkinMinerva was incorrect.

Bug: 68756
Change-Id: I332adc195ed3a7e3bd5970d86d2f2a76237fdeee