Unfortunately WebKit does not actually render the access key, so there's no way to know it's there, but it's better than not having any access key.
https://bugzilla.gnome.org/show_bug.cgi?id=761069
cc67c5f web-view: Add mnemonics for error page buttons
embed/ephy-web-view.c | 14 ++++++++++++--
src/resources/error.html | 2 +-
2 files changed, 13 insertions(+), 3 deletions(-)
Upstream: git.gnome.org