emberjs/ember.js — pull request #9919 by machty (2014-12-15 01:43:48+00:00)
Title: [FEATURE "ember-routing-transitioning-classes”]

Disables eager URL updates during slow transitions in favor of new CSS classes
added to `link-to`s (in addition to `active` class):

- `transitioning-in`: link-to is not currently active, but will be
when the current underway (slow) transition completes.
- `transitioning-out`: link-to is currently active, but will no longer
be active when the current underway (slow) transition completes.