angular/angular.dart — pull request #1070 by pavelgj (2014-05-26 17:30:59+00:00)
Title: feat(router): added vetoable preLeave event

BREAKING CHANGE

Previously, vetoing was allowed on leave (RouteLeaveEvent) which caused
issues because routes had no way to recover from other route vetoing a leave
event.

Now, similar to preEnter and enter, leave event was split into vetoable
preLeave (RoutePreLeaveEvent) and non-vetoable leave (RouteLeaveEvent).

views.configure({
'foo': ngRoute(
path: '/foo',
preLeave: (RoutePreLeaveEvent e) {
e.allowLeave(new Future.value(false));
})
});