safe-area-max-inset-* variables

[vmpstr]

Request for Mozilla Position on an Emerging Web Specification

Specification title: safe-area-max-inset-* variables
Specification or proposal URL (if available): https://drafts.csswg.org/css-env-1/#safe-area-max-insets
Proposal author(s) (@-mention GitHub accounts): @flackr @bramus
WebKit standards-position: WebKit/standards-positions#454
TAG: w3ctag/design-reviews#1046
Other information
This proposal adds safe-area-max-inset-* variables that have the value of the max possible value of the safe-area-inset-* variables. This can be used to create a different effect (a bottom bar that slides) while still respecting the safe area insets and while remaining composited.

See further discussion on: w3c/csswg-drafts#11019

/cc @emilio