Filed by: btara [at] mozilla.com
Parsed log: https://treeherder.mozilla.org/logviewer.html#?job_id=270547193&repo=mozilla-central
Full log: https://queue.taskcluster.net/v1/task/P53b4zmFSvGg1kjW3S3aIQ/runs/0/artifacts/public/logs/live_backing.log

[task 2019-10-10T00:02:56.340Z] 00:02:56 INFO - TEST-START | accessible/tests/mochitest/name/test_general.xul
[task 2019-10-10T00:02:56.506Z] 00:02:56 INFO - TEST-INFO | started process screenshot
[task 2019-10-10T00:02:56.748Z] 00:02:56 INFO - TEST-INFO | screenshot: exit 0
[task 2019-10-10T00:02:56.749Z] 00:02:56 INFO - Buffered messages logged at 00:02:56
[task 2019-10-10T00:02:56.751Z] 00:02:56 INFO - must wait for load
[task 2019-10-10T00:02:56.754Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_simple_aria_label'
[task 2019-10-10T00:02:56.755Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_both_aria_labels'
[task 2019-10-10T00:02:56.757Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_labelledby_text'
[task 2019-10-10T00:02:56.758Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_labelledby_texts'
[task 2019-10-10T00:02:56.760Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'rememberHistoryDays'
[task 2019-10-10T00:02:56.763Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'historyDays'
[task 2019-10-10T00:02:56.765Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'rememberAfter'
[task 2019-10-10T00:02:56.766Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_labelledby_mixed'
[task 2019-10-10T00:02:56.767Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_labelledby_mixed_menulist'
[task 2019-10-10T00:02:56.768Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_labelledby_mixed_hidden_child'
[task 2019-10-10T00:02:56.772Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_labelledby_mixed_hidden'
[task 2019-10-10T00:02:56.774Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_labelattr'
[task 2019-10-10T00:02:56.775Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'li_nsIDOMXULSelectControlItemElement'
[task 2019-10-10T00:02:56.776Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'box_not_nsIDOMXULSelectControlElement'
[task 2019-10-10T00:02:56.779Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_label_1'
[task 2019-10-10T00:02:56.780Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_label_2'
[task 2019-10-10T00:02:56.783Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_label_3'
[task 2019-10-10T00:02:56.784Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'btn_label_4'
[task 2019-10-10T00:02:56.785Z] 00:02:56 INFO - TEST-PASS | accessible/tests/mochitest/name/test_general.xul | Wrong name of the accessible for 'box_label_anon1'
[task 2019-10-10T00:02:56.788Z] 00:02:56 INFO - Buffered messages finished
[task 2019-10-10T00:02:56.795Z] 00:02:56 INFO - TEST-UNEXPECTED-FAIL | accessible/tests/mochitest/name/test_general.xul | uncaught exception - TypeError: textboxAcc is null at doTest@chrome://mochitests/content/a11y/accessible/tests/mochitest/name/test_general.xul:119:9
[task 2019-10-10T00:02:56.795Z] 00:02:56 INFO - setTimeout handlerSimpleTest_setTimeoutShim@chrome://mochikit/content/tests/SimpleTest/SimpleTest.js:686:43
[task 2019-10-10T00:02:56.796Z] 00:02:56 INFO - addA11yLoadEvent/waitForDocLoad/<@chrome://mochitests/content/a11y/accessible/tests/mochitest/common.js:163:14
[task 2019-10-10T00:02:56.797Z] 00:02:56 INFO - setTimeout handlerSimpleTest_setTimeoutShim@chrome://mochikit/content/tests/SimpleTest/SimpleTest.js:686:43
[task 2019-10-10T00:02:56.797Z] 00:02:56 INFO - waitForDocLoad@chrome://mochitests/content/a11y/accessible/tests/mochitest/common.js:153:12
[task 2019-10-10T00:02:56.798Z] 00:02:56 INFO - SimpleTest.waitForFocus/waitForFocusInner/focusedOrLoaded/<@chrome://mochikit/content/tests/SimpleTest/SimpleTest.js:805:67
[task 2019-10-10T00:02:56.798Z] 00:02:56 INFO -
[task 2019-10-10T00:02:56.799Z] 00:02:56 INFO - simpletestOnerror@chrome://mochikit/content/tests/SimpleTest/SimpleTest.js:1667:24
[task 2019-10-10T00:02:56.799Z] 00:02:56 INFO - OnErrorEventHandlerNonNull*@chrome://mochikit/content/tests/SimpleTest/SimpleTest.js:1647:1
[task 2019-10-10T00:02:56.801Z] 00:02:56 INFO - GECKO(10028) | JavaScript error: chrome://mochitests/content/a11y/accessible/tests/mochitest/name/test_general.xul, line 119: TypeError: textboxAcc is null
[task 2019-10-10T00:02:56.802Z] 00:02:56 INFO - GECKO(10028) | MEMORY STAT | vsize 2104426MB | vsizeMaxContiguous 68594116MB | residentFast 460MB | heapAllocated 158MB
[task 2019-10-10T00:02:56.803Z] 00:02:56 INFO - TEST-OK | accessible/tests/mochitest/name/test_general.xul | took 167ms

I suspect this is caused by the recent changes from bug 1513325.

ntim, could you, please, take a look?

Seems that D38955 fixed this. Sorry for the ni.