Summary: Closes https://github.com/facebook/draft-js/pull/273

Differential Revision: D3147269

fb-gh-sync-id: 43877fc0a71b1f6d0d0996b8d32c97e803c6ee5e
fbshipit-source-id: 43877fc0a71b1f6d0d0996b8d32c97e803c6ee5e
(cherry picked from commit 72cc76fab1f00e7120efce2d5f7f98b6c5b2134c)