We'll stop dispatching keypress events on web contents for conforming to spec of
UI Events. Some existing tests assumes that keypress events are fired even
when non-printable keys are pressed.
This patch makes them check the pref,
"dom.keyboardevent.keypress.dispatch_non_printable_keys_only_system_group_in_content"
and only listen to keydown event instead of keypress even if the pref is true
and expected key event is not a printable key press.
MozReview-Commit-ID: 6bKoK7dsB0l
Users can block the overriding of shortcuts using the permissions tab of the page info dialog, as with other permissions. Site permissions also allows the use of permissions.default.shortcuts to block overriding shortcuts for all sites.
