Commits the pre-edit string on receipt of focus_out and reset
commands.
Patch refinements by Cody Russell <bratsche@gnome.org> and
Ek Kato <ek.kato@gmail.com>
When an application translates a key event and drop its native event
before passing to imquartz, it can't recognize the NSEvent. On this
case imquartz doesn't emit any signals such as "commit" signal so
that the application doesn't insert any text. To avoid no response,
at least imquartz should fallback to slave GtkIMContextSimple.
https://bugzilla.gnome.org/show_bug.cgi?id=694273#c27
(cherry picked from commit c064e18894)
