alexclarke@ of the CLs in the blame list, https://codereview.chromium.org/2546423002 seemed the one most likely to perturb the number of times that an XHR is invoked in a layout test. Perhaps you could triage?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ef9b9da812a50324d75d85fc49f091ffc6636bb3

commit ef9b9da812a50324d75d85fc49f091ffc6636bb3
Author: rjkroege <rjkroege@chromium.org>
Date: Thu Dec 15 22:42:34 2016

TestExpectations update: http/tests/loading/preload-img-test.html flake

http/tests/loading/preload-img-test.html is flaky on trusty

BUG= 674720 
TBR=alexclarke@chromium.org
NOTRY=true

Review-Url: https://codereview.chromium.org/2576923004
Cr-Commit-Position: refs/heads/master@{#438941}

[modify] https://crrev.com/ef9b9da812a50324d75d85fc49f091ffc6636bb3/third_party/WebKit/LayoutTests/TestExpectations

With a ToT build (including https://codereview.chromium.org/2546423002) I've not been able to make this flake in debug or release locally (I tried 500 repeats - which took a while).

Not really sure what to do about this.

Sami, any ideas?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b034403ab50b3a27bda35d6cf72efec57f2f1217

commit b034403ab50b3a27bda35d6cf72efec57f2f1217
Author: qyearsley <qyearsley@chromium.org>
Date: Tue Feb 07 17:50:47 2017

Remove flaky expectations with update-test-expectations script

The update-test-expectations script is meant to remove
flaky expectations when it appears that according to the
most recent results on the flakiness dashboard for that test,
the test is no longer flaky.

BUG= 491764 , 498539 , 575766 , 600248 ,658305, 663838 , 663840 ,663848, 663851 , 663853 , 663872 , 663874 , 663877 , 663879 ,664817,664839, 664840 , 664841 , 664842 , 664846 , 664850 , 664855 , 664856 , 666991 , 671480 , 671618 , 672204 , 673296 , 673632 , 674720 ,674858, 678488 , 683800 

Review-Url: https://codereview.chromium.org/2679543005
Cr-Commit-Position: refs/heads/master@{#448663}

[modify] https://crrev.com/b034403ab50b3a27bda35d6cf72efec57f2f1217/third_party/WebKit/LayoutTests/TestExpectations

The referred test doesn't seem to be flaky in recent runs of the bot. There was no activity in this issue since February. Marking as obsolete.