emberjs/ember.js — pull request #5619 by drogus (2014-09-21 10:19:45+00:00)
Title: Set previousValues on ChangeMeta in dependentArrayWillChange

This is an attempt to fix #5558. The problem is described there.

One thing that I'm not sure about here is if the same code should be also added to `dependentArrayDidChange`. I'm also not sure if there's any better way to test it.