Problem is: I can't repro the problem. Yesterday, I prepared a change that will allow me to RCR. So, let's get that committed and then see what happens. :)

In CQ...

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d53269bc5d01bbc8a24a9a3b0f2d1226650b71b6

commit d53269bc5d01bbc8a24a9a3b0f2d1226650b71b6
Author: Yuri Wiitala <miu@chromium.org>
Date: Wed May 31 22:49:08 2017

CastV2PerformanceTest: Split into separate promises to RCR flakiness.

On Windows perf bots, there seems to be a strange "timeout" issue with
CastV2PerformanceTests.Performance/0 (and none of the others). From the
logs, it seems one of the async extension API calls may be blocked (or
is throwing an exception). This change splits the individual ext API
calls into separate Promises, each with a separate timeout handler and
error message that will help us narrow-down the root-cause of the
flakiness.

BUG= 728206 
TBR=xjz@chromium.org

Change-Id: I7357bd9f8f5dc50b9a60c93d7a100ab64594ed3d
Reviewed-on: https://chromium-review.googlesource.com/518662
Commit-Queue: Yuri Wiitala <miu@chromium.org>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#476075}
[modify] https://crrev.com/d53269bc5d01bbc8a24a9a3b0f2d1226650b71b6/chrome/test/data/extensions/api_test/cast_streaming/performance.js

Welp, in the latest runs, things are green. Will monitor over the next few days...

Thanks for the quick fix! You rocks!

Strangely, the flake went away completely, and all the bots are green now. Maybe I inadvertently fixed something (or just changed the timing causing the flake)? Welp, if the tests go red again, feel free to re-open.