Review Mozilla 1937096: Offscreen canvases don't protect against font fingerprinting

🔍 Bugzilla Audit

Bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=1937096

Description

32ffe8df conflicts with our BB 43140: Tighten up fonts on Linux. patch (2d289208).

I think the reason is the replacement of aPresContext with aFontVisibilityProvider.

Still, I'm opening an issue for better review.

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