The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/28897f84d2d2457d38305b310a5a6ca90ea244a7

commit 28897f84d2d2457d38305b310a5a6ca90ea244a7
Author: Caleb Rouleau <crouleau@chromium.org>
Date: Tue Nov 14 23:39:20 2017

[Media Cases] Reduce noise in MSE tests by waiting until xhr completes.

This will mean that networking changes will not affect
time_to_video_play and other metrics.

Bug:  784664 
Change-Id: I73204bfcdf650ece2250361264970371544675a1
Reviewed-on: https://chromium-review.googlesource.com/767889
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Reviewed-by: Matthew Wolenetz <wolenetz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#516500}
[modify] https://crrev.com/28897f84d2d2457d38305b310a5a6ca90ea244a7/tools/perf/page_sets/media_cases/mse.js

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/05121b638fb7d738846e17d445d8c7fc7a7d3ce2

commit 05121b638fb7d738846e17d445d8c7fc7a7d3ce2
Author: Caleb Rouleau <crouleau@chromium.org>
Date: Wed Nov 15 02:06:57 2017

[Telemetry] Repeat MSE test case runs.

This reduces noise. The MSE cases are pretty noisy right now.
See https://chromeperf.appspot.com/report?sid=ea77547fca270648c54a3719118abc4a70877c94bd7da1d53e6a002f74efb9af
We only want to repeat the MSE cases, not the other tests in that benchmark.

This should add .5 (seconds/addition run) * 9 (additional runs) * 4 (test cases) = ~18 seconds

Bug:  784664 
Change-Id: Ia4862ba4e8ede1a15e5a8d5ba92e01bdb1bce5a2
Reviewed-on: https://chromium-review.googlesource.com/767896
Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#516558}
[modify] https://crrev.com/05121b638fb7d738846e17d445d8c7fc7a7d3ce2/tools/perf/page_sets/media_cases.py

Fixed. issue 784661 should be unblocked.