When you create a <key> element, which is what the commands API
does under the hood to allow keyboard shortcuts, the event type
that the handler listens to defaults to keypress. For printable
characters, the keyCode property of a keypress event is 0,
causing keycode bindings for these printable characters to not
work. We could use key for these properties, but the shift key
interacts with the key property in ways that make it simpler to
simply fix the keycode usage for our purposes.
MozReview-Commit-ID: HdWdN7cMfuq
d28db54125
