google/traceur-compiler — pull request #1145 by arv (2014-06-28 19:25:48+00:00)
Title: Fix issue with '@@iterator' in Firefox.

Since Firefox does not support symbols but they do have iterable
Map and Set implementations, using '@@iterator', our for-of loops
do not work with Firefox.

This adds Symbol.iterator to Map.prototype and Set.prototype

Fixes #1142
Fixes #1144