emberjs/ember.js — pull request #5277 by stefanpenner (2014-07-29 22:36:02+00:00)
Title: improve iterDeps in some scenarios by 20-30% in v8, no noticeable downsi...

...des in other evergreen browsers

1. don’t enumerate keys, if no deps exist to produce keys
2. in v8 for (x in y) where y is non enumerable deopts entire function [readmore](https://github.com/petkaantonov/bluebird/wiki/Optimization-killers#5-for-in)