This test is already disabled on Linux due to being to slow on some of the bots (MSAN) and timing out. Since it is experiencing timeouts on Windows as well, I will disable for it Windows. See issue 729136 for the MSAN timeouts. Also it is marked as flaky in the web-platform-tests repository.

Assigning to mmenke as this is network related, please reassign to someone more appropriate on the Blink side if needed.

I'm not going to have time for this.  I don't know MSAN or the WPT tests, and our mime sniffing browser_tests and unittests are passing without a problem.

How about adding the test to SlowTests?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f6f161284dd9ebb47317badf9e07cf1499038bb4

commit f6f161284dd9ebb47317badf9e07cf1499038bb4
Author: clamy <clamy@chromium.org>
Date: Wed Jan 10 17:03:57 2018

Mark layout test as flaky

external/wpt/mimesniff/mime-types/parsing.any.worker.html is timeouting
on Windows 7 bots in a flaky manner. Marking it as such.

TBR=mmenke@chromium.org

Bug:  800359 
Change-Id: I2eaa93c206b981970db1fb5f335a6881f4963ccc
Reviewed-on: https://chromium-review.googlesource.com/857506
Reviewed-by: Camille Lamy <clamy@chromium.org>
Commit-Queue: Camille Lamy <clamy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#528342}
[modify] https://crrev.com/f6f161284dd9ebb47317badf9e07cf1499038bb4/third_party/WebKit/LayoutTests/TestExpectations

Perhaps we should mark the test [ Slow ]  in SlowTests instead of [ Pass Timeout ] in TestExpectations.

I don't suppose we know if it's just slow or broken?  If we have evidence it's broken, that seems more worth investigating than if it's just slow.

It looks like slow based on the flakiness dashboard: https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests&tests=external%2Fwpt%2Fmimesniff%2Fmime-types%2Fparsing.any.worker.html

We can verify by adding Slow to the current expectation and see if it still timeout.

+robertma@ who added META: timeout=long to the test.

https://github.com/w3c/web-platform-tests/commit/497047516c777f76833febad1f5df86eef6a8c06

"META: timeout=long" already gives the test extra time (i.e. equivalent to [ Slow ]). There's a bug (issue 801202) that we still list these tests under "slowest tests that are not marked as SLOW and did not timeout/crash", which is confusing.

I knew the test was slow, so I added that META in the upstream. Then I noticed it still timed out on the MSAN bot, so I marked it as [ Pass Timeout ] in MSANExpectations. Now it seems like it also times out on normal Windows bots... So yes, we should mark it as [ Pass Timeout ] on [ Win ].

Of course, if someone is familiar with mimesniff and has the time, it'd be good to look into the test and see if it can be split/sped up (or if there are outright bugs).

Glancing at the test, I have no idea what it's actually doing, but it looks like it may be making about 800 blobs, and checking their types, and never makes any requests that go through the network stack.  So this is likely more related to creating 800 blobs (And 800 "Files", whatever those are) and getting their types, rather than mime sniffing.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7ca9f2b6297f85874f5efe2a03fd065082b4f1d7

commit 7ca9f2b6297f85874f5efe2a03fd065082b4f1d7
Author: Robert Ma <robertma@chromium.org>
Date: Mon Jan 15 19:21:53 2018

Mark mimesniff/mime-types/parsing.any.html as flaky

This test shares the same source file as
mimesniff/mime-types/parsing.any.worker.html, which is already known to
be flaky.

TBR=yhirano

Bug:  800359 
Change-Id: I94c26594245bffea4a6f5c0a819807015cfc014c
No-Try: True
Reviewed-on: https://chromium-review.googlesource.com/867411
Reviewed-by: Robert Ma <robertma@chromium.org>
Commit-Queue: Robert Ma <robertma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#529318}
[modify] https://crrev.com/7ca9f2b6297f85874f5efe2a03fd065082b4f1d7/third_party/WebKit/LayoutTests/TestExpectations

Detected 3 new flakes for test/step "external/wpt/mimesniff/mime-types/parsing.any.worker.html". To see the actual flakes, please visit https://chromium-try-flakes.appspot.com/all_flake_occurrences?key=ahVzfmNocm9taXVtLXRyeS1mbGFrZXNyRAsSBUZsYWtlIjlleHRlcm5hbC93cHQvbWltZXNuaWZmL21pbWUtdHlwZXMvcGFyc2luZy5hbnkud29ya2VyLmh0bWwM. This message was posted automatically by the chromium-try-flakes app. Since flakiness is ongoing, the issue was moved back into Sheriff Bug Queue (unless already there).

Marking them slow in https://chromium-review.googlesource.com/c/chromium/src/+/886704

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ca91e7d0fceae42b489bb5e09d17e0782917e43e

commit ca91e7d0fceae42b489bb5e09d17e0782917e43e
Author: Vasilii Sukhanov <vasilii@chromium.org>
Date: Thu Jan 25 15:27:02 2018

Mark 2 WPT tests as slow

external/wpt/mimesniff/mime-types/parsing.any.html
external/wpt/mimesniff/mime-types/parsing.any.worker.html

TBR=ortuno@chromium.org

Bug:  800359 
Change-Id: I139aa13a2484fba22e8db3fca8f4b3a38ca2a506
Reviewed-on: https://chromium-review.googlesource.com/886704
Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Commit-Queue: Vasilii Sukhanov <vasilii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531902}
[modify] https://crrev.com/ca91e7d0fceae42b489bb5e09d17e0782917e43e/third_party/WebKit/LayoutTests/SlowTests
[modify] https://crrev.com/ca91e7d0fceae42b489bb5e09d17e0782917e43e/third_party/WebKit/LayoutTests/TestExpectations