angular/angular.js — pull request #2020 by provegard (2013-02-15 23:34:55+00:00)
Title: fix(ngClass): keep track of old ngClass value manually

ngClassWatchAction, when called as a $watch function, gets the wrong old
value after it has been invoked previously due to observation of the
interpolated class attribute. As a result it doesn't remove classes
properly. Keeping track of the old value manually seems to fix this.

Fixes #1637