This seems to start with the landing of bug 1524655. :lina could you, please, take a look?
Bug 1274773 Comment 55 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
This seems to start with the landing of bug 1524655. https://treeherder.mozilla.org/#/jobs?repo=autoland&searchStr=windows%2C7%2Cdebug%2Cmochitests%2Cwith%2Ce10s%2Ctest-windows7-32%2Fdebug-mochitest-e10s-2%2Cm-e10s%282%29&group_state=expanded&fromchange=fa6af8c14ee45a20df4c3f83286b85874082f877&tochange=f28acbccbc62a92d3116b30f35afcd7203ff07d7&selectedJob=234424024 :lina could you, please, take a look?