We don't normally use px values for font-sizes, because OSes have different defaults and even offer customizing the default font size. Instead we use em to make text relatively smaller or bigger.

Also note that because the urlbar's font size is different across platforms, the current px values will look more or less inconsistent depending on the OS.

Make #urlbar-contextual-tip inherit its font size so that it's the same as the size used for other results. Set #urlbar-contextual-tip-button's font size to 1em to override the smaller <button> default font size.

https://hg.mozilla.org/mozilla-central/rev/982bb9015f79

Comment on attachment 9091220 [details]
Bug 1576888 - Stop using px values for #urlbar-contextual-tip's and #urlbar-contextual-tip-button's font sizes.

Beta/Release Uplift Approval Request

• User impact if declined: We may want to run an experiment on 70 that would use this patch.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: No
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: Bug 1576889 must be uplifted first
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): It's a trivial CSS patch. This UI isn't even visible in Firefox by default. It would only be shown in an experiment.
• String changes made/needed: None

Comment on attachment 9091220 [details]
Bug 1576888 - Stop using px values for #urlbar-contextual-tip's and #urlbar-contextual-tip-button's font sizes.

CSS change to support an experiment on 70. OK for uplift to beta 7.

https://hg.mozilla.org/releases/mozilla-beta/rev/57a4edf435a71b6a13c1217d81718391124cb2c7