Filed by: rgurzau [at] mozilla.com https://treeherder.mozilla.org/logviewer.html#?job_id=155956750&repo=mozilla-inbound https://queue.taskcluster.net/v1/task/YMUD5OjsQHK45PKEgmJ8ug/runs/0/artifacts/public/logs/live_backing.log 16:16:17 INFO - GECKO(3640) | 1515773777349 addons.xpi DEBUG removeTemporaryFile: https://example.com/browser/toolkit/mozapps/extensions/test/xpinstall/redirect.sjs?mode=redirect removing temp file C:\Users\GenericWorker\AppData\Local\Temp\tmp-ptq.xpi 16:16:17 INFO - GECKO(3640) | Assertion failure: !mTransparentSurface && !mMemoryDC, at z:/build/build/src/widget/windows/WinCompositorWidget.cpp:256 16:16:30 INFO - GECKO(3640) | #01: mozilla::widget::WinCompositorWidget::CreateTransparentSurface(mozilla::gfx::IntSizeTyped<mozilla::gfx::UnknownUnits> const &) [widget/windows/WinCompositorWidget.cpp:256]

This doesn't make a whole lot of sense. The assertion tripped in WinCompositorWidget::CreateTransparentSurface should not be happening because we are getting called from WinCompositorWidget::EnsureTransparentSurface which explicitly sets mTransparentSurface and mMemoryDC to nullptr before calling (added in bug 1289236.)