The new test plays a short audio file and verifies that the page
finishes playing it.

Bug: 1027048
Change-Id: I58a83098812c0e1b280a7ead5fdc7579b827d368
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1928116Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Auto-Submit: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718248}