Editorial: clean up condition logic in navigate event firing

"commit a navigate event" is a noop when the navigation is not
intercepted in the first place.

Instead of calling it and checking for the interception state
internally, only call it for intercepted navigations, and rename it
to "commit an intercepted navigate event". Also remove internal
logic that tests whether the navigation is same-document
(intercepted navigations are always same-document).

Author: noamr