These represent <nowiki> tags. If the user doesn't edit the text inside
the nowiki, we round-trip the <span typeof="mw:Nowiki"> wrapper cleanly,
but if they do edit it, we unwrap it. This then triggers re-escaping
in Parsoid, and prevents cases where the user edits the text to no
longer need escaping but Parsoid still wraps it in <nowiki> because
of the <span typeof="mw:Nowiki"> wrapper.
In order to detect whether the contents have changed, the nowiki
annotation stores a copy of its contents. To avoid infinite recursion,
we have to exclude this attribute for hash generation.
Bug: 47678
Change-Id: I2edc46b6d87d2f91e952efcb09c0edae5166958f
