Same issue for me after rebooting this morning (did the update last night).
Found a solution that worked for me on this thread (using google cache, because for whatever reason the topic doesn't seem to existe anymore)
So I downgraded webkit2gtk to 2.14.2-2 instead of the current 2.14-3-1 and it worked for me
pacman -U /var/cache/pacman/pkg/webkit2gtk-2.14.2-2-x86_64.pkg.tar.gz
Doesn't sound like a real solution to me but absolutely need to work this morning so I'll look further into this issue later.