OK, well, on a second look, this is the failure we're looking for: https://treeherder.mozilla.org/#/jobs?repo=try-comm-central&revision=ce4ff9f81da7f71cc3a182c4ffab9ad840414866&selectedJob=241920641 Since bug 1509837 was already backed out, it must have been bug 1512805, but it's still unclear why that got aggravated more later.
Bug 1546130 Comment 4 Edit History
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OK, well, on a second look, this is the failure we're looking for: https://treeherder.mozilla.org/#/jobs?repo=try-comm-central&revision=ce4ff9f81da7f71cc3a182c4ffab9ad840414866&selectedJob=241920641 Since bug 1509837 was already backed out, it must have been bug 1512805, but it's still unclear why that got aggravated more later. EDIT: And lately, it's only failing on Windows.