Re: [webmessaging-tests] Fix test flakiness caused by not waiting for an iframe to load. (#4301)

> Please squash and finish your commit message.

Squashed, and fixed commit message.

View on GitHub: https://github.com/w3c/web-platform-tests/pull/4301#issuecomment-265880344

Received on Thursday, 8 December 2016 22:56:27 UTC