The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a6c1ac82abcd0247a8f598737ecdb4e53e665cf3

commit a6c1ac82abcd0247a8f598737ecdb4e53e665cf3
Author: johnme <johnme@chromium.org>
Date: Thu Feb 02 13:48:02 2017

Mark external/wpt/quirks-mode/unitless-length.html as flaky timeout

https://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=external%2Fwpt%2Fquirks-mode%2Funitless-length.html&testType=webkit_tests

BUG= 646133 , 687442 
TBR=qyearsley@chromium.org
NOTRY=true
NOTREECHECKS=true

Review-Url: https://codereview.chromium.org/2676623002
Cr-Commit-Position: refs/heads/master@{#447756}

[modify] https://crrev.com/a6c1ac82abcd0247a8f598737ecdb4e53e665cf3/third_party/WebKit/LayoutTests/TestExpectations

This is still an issue. Recent instance:  bug 699181 .

Another case:

An expectation for external/wpt/pointerevents/compat/pointerevent_touch-action_two-finger_interaction-manual.html was removed in https://chromium-review.googlesource.com/c/454857/2.

As of right now, I'm still not sure why this happens, but I think I could probably reproduce this by making another manual import, running wpt-update-expectations, and finding a place where it happens.

Here's one idea about what's happening:

When a test flakily passes, it is still fetched along with other "failing" tests at WPTExpectationsUpdater.get_failing_results_dict:
https://cs.chromium.org/chromium/src/third_party/WebKit/Tools/Scripts/webkitpy/w3c/wpt_expectations_updater.py?l=77

And then, if it's a testharness test, then in WPTExpectationsUpdater.get_tests_to_rebaseline, this test is added to the list of tests that should be rebaselined.

Then, in webkit-patch rebaseline-cl, when the passing test is rebaselined, and there are actually no new baselines to download since the test is now passing, the line is removed from TestExpectations while rebaselining.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fb5a41a23dda1f926f1d724650ad63d22bb823ac

commit fb5a41a23dda1f926f1d724650ad63d22bb823ac
Author: qyearsley <qyearsley@chromium.org>
Date: Fri Mar 17 01:29:53 2017

In wpt-update-expectations, ignore tests that unexpectedly pass.

In general, when the auto-importer is updating expectations and baselines, if a test unexpectedly passes, then it should be OK to just leave it alone and not update anything.

If the pass was a flaky pass, then the previous behavior would have been to try to rebaseline it, which would remove the expectation, which would later cause trouble if the test is flaky.

BUG= 687442 

Review-Url: https://codereview.chromium.org/2750273003
Cr-Commit-Position: refs/heads/master@{#457647}

[modify] https://crrev.com/fb5a41a23dda1f926f1d724650ad63d22bb823ac/third_party/WebKit/Tools/Scripts/webkitpy/w3c/wpt_expectations_updater.py
[modify] https://crrev.com/fb5a41a23dda1f926f1d724650ad63d22bb823ac/third_party/WebKit/Tools/Scripts/webkitpy/w3c/wpt_expectations_updater_unittest.py

Possibly fixed, will reopen if I see this again!