Sorry I should have done this sooner to avoid wasting 3 days on this review, but I just looked at it and I'd feel more comfortable if Matteo reviewed it instead of me.

Gabriel, sorry I didn't notice this bug until few hours ago! I was working anyway to a deep refactoring to `moveInfobar` that you've basically reused. Since the current logic in `moveInfobar` is broken (as we saw during the work week in Paris), you want to probably rewrite your code on top of bug 1349275 (once reviewed) that fixes that, but also changes completely how the infobar is working now. I tried to be exhaustive in the comment why that was needed, and how to fix other highlighters that uses the infobar (e.g. the css-grid). Therefore I'm canceling the review flag for the moment, until we can updated the css-grid's infobars. Let me know if it's okay to you!

Passing this over to you zer0

Comment on attachment 8867658 [details] Bug 1348919 - forced grid cell infobar and area infobar position; https://reviewboard.mozilla.org/r/139248/#review142544

Pushed by mferretti@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/161b368464fb forced grid cell infobar and area infobar position; r=gl