[css-2025][css-easing-2] Add `linear()` to Safe to Release exceptions

[SebastianZ]

Splitting the discussion from #10687 for adding the linear() function from CSS Easing 2 to the Safe to Release pre-CR Exceptions section of the CSS Snapshot 2025.

Data to consider:

• Spec. status: FPWD (published: 29 August 2024)
• See also [css-easing-2] Is linear() easing in a shippable state? #7533
• implemented in all major browsers since 2023
• WPT: passing tests (experimental): Chrome: 29, Edge: 29, Firefox: 29, Safari: 40; interop: 28 / 41 (68,2%)
• Open issues: on GitHub: 1, in spec.: 0

Summary: High interoperability, some open issues

Sebastian

[css-meeting-bot]

The CSS Working Group just discussed [css-2025][css-easing-2] Add `linear()` to Safe to Release exceptions.

The full IRC log of that discussion

<florian> SebastianZ: there was an issue about whether it is in shippable state, and we resolved it is
<florian> SebastianZ: implemented across browsers since 2023
<florian> SebastianZ: interop is not that high (68%), but we already said it's fine
<florian> SebastianZ: just one open issue on github, none in the spec
<florian> astearns: the shipable state issue said OK for FPWD, but did not say OK to ship
<florian> SebastianZ: Ah, right
<florian> SebastianZ: does someone remember if we discussed shipability, or publication only?
<florian> astearns: seems we only discussed publishing first
<florian> florian: so the precondition is fulfilled, but is the feature good enough?
<florian> astearns: test pass rate seems low, I am not OK with putting it in safe to release
<florian> astearns: test results show lack of interop
<florian> SebastianZ: safe-to-release is supposed to be about spec status, not interop
<florian> astearns: editor said it's good
<florian> astearns: I'm leaning to not yet
<florian> fantasai: the test seems to be largely about specified value, not behavior
<florian> fantasai: doesn't seem like a big deal
<florian> astearns: I just don't feel confident