Disable flaky test: media/video-played-collapse.html

This test caused a recent good change to be reverted because the
flakiness tilted more towards "constant failure" on Mac 10.13 (see
https://chromium-review.googlesource.com/c/chromium/src/+/1509365).

According to the Flake Portal (and running the test on a clean checkout
on my local Linux and Mac machines), the test indeed is flaky.

TBR=chcunningham@chromium.org

Bug: 931533
Change-Id: I368b171a69ce423e47810c77ab0346bc8286c7cf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1509633Reviewed-by: Yuri Wiitala <miu@chromium.org>
Commit-Queue: Yuri Wiitala <miu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638751}

third_party/blink/web_tests/TestExpectations

@@ -6025,3 +6025,7 @@ crbug.com/938780 [ Mac ] external/wpt/animation-worklet/worklet-animation-with-s
 # Sheriff 2019-03-06
 crbug.com/938591 [ Linux ] fast/events/middleClickAutoscroll-nested-divs-forbidden.html [ Failure Pass ]
 crbug.com/938884 [ Win7 Mac ] http/tests/devtools/elements/styles-3/styles-add-blank-property.js [ Pass Timeout ]
+
+# Caused a revert of a good change.
+crbug.com/931533 media/video-played-collapse.html [ Pass Failure ]
+crbug.com/931533 virtual/video-surface-layer/media/video-played-collapse.html [ Pass Failure ]