emberjs/ember.js — pull request #4217 by machty (2014-01-23 18:59:11+00:00)
Title: [NICETHING beta] helpful whitespace classNameBindings assert

I've trolled myself many times thinking that classNameBindings works with a
space separated string
(probably because of how bind-attr class="" works). This should help me never
troll myself again.

/cc @ebryn