openlayers/ol3 — pull request #2865 by elemoine (2014-10-23 19:30:30+00:00)
Title: Add old value to property change events

This PR adds an `oldValue` property to `ol.ObjectEvent`, which holds the value before the change happened.

I'll try to update https://github.com/openlayers/ol3/pull/2841 based on this changed.