[chromium] Layout Test media/media-document-audio-repaint.html is flaky

[chromium] Layout Test media/media-document-audio-repaint.html is flaky
https://bugs.webkit.org/show_bug.cgi?id=76580

Reviewed by James Robinson.

Make sure to call layoutTestController.display() at a stable point
(namely when the media element is paused) so that any subsequent GPU
disabling doesn't cause a complete redraw (and the test to be
flaky).

* media/media-document-audio-repaint.html:
* platform/chromium/test_expectations.txt:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@107721 268f45cc-cd09-0410-ab3c-d52691b4dbfc