Upstream service worker message event tests to WPT
This patch corrects invalid assertions relating to the `ports` property
described by the ExtendableMessageEvent API (see crbug.com/702352 and
crbug.com/702361). It also re-formats the tests to improve test precision (by
reducing reliance on the `toString` operation) and more closely align with the
patterns used within the Web Platform Tests project.
BUG=688116,702352,702361
R=falken@chromium.org
Review-Url: https://codereview.chromium.org/2751113005
Cr-Commit-Position: refs/heads/master@{#459099}
14 files changed
