Firefox 69: CSS ::cue limitations enforced (#4571)
Firefox 69: CSS ::cue limitations enforced (#4571)

* Firefox 69: ::cue now limits permitted properties per spec
Previously, `::cue` allowed pretty much anything. Now the allowed
properties are limited per the spec.

Source:
* https://bugzilla.mozilla.org/show_bug.cgi?id=1321488

* Revert "Firefox 69: ::cue now limits permitted properties per spec"

This reverts commit 34712b7525e5cbc65b0c58e1bcee4a2ded404c44. Pushed
to the wrong branch.

* Firefox 69: ::cue now enforces CSS property restrictions
Previously, `::cue` did not enforce the limitations on what CSS
properties you could use in a WebVTT cue. Now those limitations
are properly enforced.

Source:
* https://bugzilla.mozilla.org/show_bug.cgi?id=1321488

mdn/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data,chrisdavidmills/browser-compat-data