binding: Adds layout tests to check origins of window.postMessage

Imports EventListener-incumbent-global tests from w3c/web-platform-tests.
The tests show the current status of support of postMessage's origins.

The original tests are here:
https://github.com/w3c/web-platform-tests/blob/master/dom/events/EventListener-incumbent-global-1.sub.html
https://github.com/w3c/web-platform-tests/blob/master/dom/events/EventListener-incumbent-global-2.sub.html

BUG=612458,622974

Review-Url: https://codereview.chromium.org/2142173003
Cr-Commit-Position: refs/heads/master@{#405428}
7 files changed