There's a heavy enough overhead to going through XPConnect for
every observer for every visit on the nsINavHistoryObserver
interface, so this patch reduces that by replacing the single-
visit notification with one which accepts an array of visits.
Some notes: To avoid problems with the orderings of the various
ways in which we notify about visits, we have to send our bulk
onVisits notification before doing any of the others. This does
mean it technically behaves slightly different than the prior
approach of interleaving the notifications, but I can't find any
way in which this has any consequences to the end result, and it
doesn't break any tests.
MozReview-Commit-ID: GdeooH8mCkg
5394d406e4