Fix 'yankshort' for YouTube.
Fix 'yankshort' for YouTube.

Only full page requests currently appear to update link[rel='shortlink'].

Fixes issue #1074.

Kjwon15/dactyl,madand/pentadactyl-pm,moonshadow/dactyl,5digits/dactyl,5digits/dactyl,5digits/dactyl,moonshadow/dactyl,madand/pentadactyl-pm,Kjwon15/dactyl,nathyong/dactyl,airodactyl/dactyl,invl/dactyl,nathyong/dactyl,5digits/dactyl,airodactyl/dactyl,nathyong/dactyl,Kjwon15/dactyl,airodactyl/dactyl,madand/pentadactyl-pm,moonshadow/dactyl,airodactyl/dactyl,invl/dactyl,nathyong/dactyl,Kjwon15/dactyl,airodactyl/dactyl,invl/dactyl,Kjwon15/dactyl,moonshadow/dactyl,Kjwon15/dactyl,5digits/dactyl,invl/dactyl,moonshadow/dactyl,madand/pentadactyl-pm,nathyong/dactyl,madand/pentadactyl-pm,invl/dactyl,airodactyl/dactyl,invl/dactyl,5digits/dactyl,madand/pentadactyl-pm,nathyong/dactyl,moonshadow/dactyl