openlayers/ol3 — pull request #678 by tschaub (2013-04-30 21:00:02+00:00)
Title: Rename onOnce to once

Prior art:

* Node's [`Emitter#once()`](http://nodejs.org/api/events.html#events_emitter_once_event_listener)
* Backbone's [`Events#once()`](http://backbonejs.org/#Events-once)