Filed by: rmaries [at] mozilla.com
Parsed log: https://treeherder.mozilla.org/logviewer.html#?job_id=302649869&repo=autoland
Full log: https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/D16b1HztSDynJsyHv0QQZA/runs/0/artifacts/public/logs/live_backing.log

[task 2020-05-17T20:02:57.456Z] 20:02:57 INFO - TEST-START | remote/test/browser/network/browser_responseReceived.js
[task 2020-05-17T20:03:05.218Z] 20:03:05 INFO - TEST-PASS | remote/test/browser/network/browser_responseReceived.js | Page.navigate returned a frameId -
[task 2020-05-17T20:03:05.218Z] 20:03:05 INFO - Wait for Network events
[task 2020-05-17T20:03:05.219Z] 20:03:05 INFO - Buffered messages finished
[task 2020-05-17T20:03:05.220Z] 20:03:05 INFO - TEST-UNEXPECTED-FAIL | remote/test/browser/network/browser_responseReceived.js | Expected number of Network.responseReceived events - Got 1, expected 2
[task 2020-05-17T20:03:05.221Z] 20:03:05 INFO - Stack trace:
[task 2020-05-17T20:03:05.224Z] 20:03:05 INFO - chrome://mochikit/content/browser-test.js:test_is:1327
[task 2020-05-17T20:03:05.224Z] 20:03:05 INFO - chrome://mochitests/content/browser/remote/test/browser/network/browser_responseReceived.js:documentNavigationWithResource:41
[task 2020-05-17T20:03:05.225Z] 20:03:05 INFO - chrome://mochitests/content/browser/remote/test/browser/head.js:fn:69
[task 2020-05-17T20:03:05.225Z] 20:03:05 INFO - chrome://mochikit/content/browser-test.js:Tester_execTest/<:1064
[task 2020-05-17T20:03:05.226Z] 20:03:05 INFO - chrome://mochikit/content/browser-test.js:Tester_execTest:1104
[task 2020-05-17T20:03:05.226Z] 20:03:05 INFO - chrome://mochikit/content/browser-test.js:nextTest/<:927
[task 2020-05-17T20:03:05.227Z] 20:03:05 INFO - chrome://mochikit/content/tests/SimpleTest/SimpleTest.js:SimpleTest.waitForFocus/waitForFocusInner/focusedOrLoaded/<:918
[task 2020-05-17T20:03:05.229Z] 20:03:05 INFO - TEST-PASS | remote/test/browser/network/browser_responseReceived.js | Got the doc response -
[task 2020-05-17T20:03:05.229Z] 20:03:05 INFO - TEST-PASS | remote/test/browser/network/browser_responseReceived.js | Doc response has expected mimeType -
[task 2020-05-17T20:03:05.230Z] 20:03:05 INFO - TEST-PASS | remote/test/browser/network/browser_responseReceived.js | The doc response has 'Document' type -
[task 2020-05-17T20:03:05.232Z] 20:03:05 INFO - TEST-PASS | remote/test/browser/network/browser_responseReceived.js | The doc request has requestId = loaderId -
[task 2020-05-17T20:03:05.235Z] 20:03:05 INFO - TEST-PASS | remote/test/browser/network/browser_responseReceived.js | Doc response returns same frameId as Page.navigate -
[task 2020-05-17T20:03:05.236Z] 20:03:05 INFO - TEST-PASS | remote/test/browser/network/browser_responseReceived.js | Doc response has headers -
[task 2020-05-17T20:03:05.237Z] 20:03:05 INFO - TEST-PASS | remote/test/browser/network/browser_responseReceived.js | Doc response status is 200 -
[task 2020-05-17T20:03:05.238Z] 20:03:05 INFO - TEST-PASS | remote/test/browser/network/browser_responseReceived.js | Doc response status is OK -
[task 2020-05-17T20:03:05.238Z] 20:03:05 INFO - TEST-PASS | remote/test/browser/network/browser_responseReceived.js | Doc response has expected protocol -
[task 2020-05-17T20:03:05.239Z] 20:03:05 INFO - CDP client closed
[task 2020-05-17T20:03:05.241Z] 20:03:05 INFO - GECKO(3765) | 1589745784727 RemoteAgent TRACE <-(connection {428dee40-1843-4eb3-aa45-65063b548753}) {"method":"Target.targetDestroyed","params":{"targetId":"a13d5c28-202e-4a29-a821-c20e4ba8ed7a"}}
[task 2020-05-17T20:03:05.244Z] 20:03:05 INFO - GECKO(3765) | 1589745784728 RemoteAgent TRACE <-(connection {428dee40-1843-4eb3-aa45-65063b548753}) {"method":"Target.targetDestroyed","params":{"targetId":"8020666b-abe2-4615-b4f3-581cd07229a5"}}
[task 2020-05-17T20:03:05.244Z] 20:03:05 INFO - GECKO(3765) | 1589745784728 RemoteAgent TRACE <-(connection {428dee40-1843-4eb3-aa45-65063b548753}) {"method":"Target.targetDestroyed","params":{"targetId":"51f106bc-d007-4ddf-a5dd-a53573bcd135"}}
[task 2020-05-17T20:03:05.247Z] 20:03:05 INFO - CDP server stopped
[task 2020-05-17T20:03:05.247Z] 20:03:05 INFO - GECKO(3765) | [Child 4084: Main Thread]: I/DocShellAndDOMWindowLeak --DOCSHELL 0x7fcd76428400 == 0 [pid = 4084] [id = {77b9b6cf-1357-4398-a846-e34607459d6c}] [url = http://example.com/browser/remote/test/browser/network/doc_networkEvents.html]
[task 2020-05-17T20:03:05.248Z] 20:03:05 INFO - GECKO(3765) | [Child 4084: Main Thread]: I/DocShellAndDOMWindowLeak --DOMWINDOW == 3 (0x7fcd76d92000) [pid = 4084] [serial = 20] [outer = (nil)] [url = about:blank]
[task 2020-05-17T20:03:05.249Z] 20:03:05 INFO - GECKO(3765) | [Child 4084: Main Thread]: I/DocShellAndDOMWindowLeak --DOMWINDOW == 2 (0x7fcd76429400) [pid = 4084] [serial = 19] [outer = (nil)] [url = about:blank]
[task 2020-05-17T20:03:05.249Z] 20:03:05 INFO - Not taking screenshot here: see the one that was previously logged

Regressed by bug 1552324.

Maybe I can fix it while working on bug 1637363.

Looks like a too short timeout for the events. Might be fixed with the patch on bug 1638196.

No more failure since May 27th. So it's fixed by my patch on bug 1638196.