Make DOMTokenList.prototype.toString enumerable.

As 'stringifier' implies an enumerable toString(), drop the use
of [NotEnumerable] for DOMTokenList's. This also aligns with other
implementations (FF, Edge.)

R=yoav@yoav.ws, philipj@opera.com
BUG=306606

Review URL: https://codereview.chromium.org/1916453002

Cr-Commit-Position: refs/heads/master@{#389442}
2 files changed