[css-grid] Introduce a "forced" version of the `fr` unit.

[Dan503]

In issue #1777, It was recognized that authors would really like it if 1fr actually meant minmax(0,1fr) rather than minmax(min-content,1fr) which is what it essentially means right now.

It was closed due to it being too hazardous to change the meaning of the fr unit at that point in time.

What I am suggesting is that a new unit be introduced that does equal minmax(0,1fr). I'm thinking an efr unit (short for "equal fraction").

It's really cumbersome writing out minmax(0,1fr) all the time. It would be much nicer if we could write 1efr instead.

The conversation in issue #2270 (comment) also makes note of the need for an easier way to write equal fractions.

Spec link for the fr unit:
https://www.w3.org/TR/css-grid-1/#fr-unit

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Update

I've changed my mind about the unit name. I believe it should be named ffr now instead of efr so that it implies "forced fraction" instead of "equal fraction"

Reasons explained in this comment:
#2677 (comment)

[fantasai]

Let's see if we can fix #1865 and if that solves the problem first. :)

[Dan503]

I have changed my mind about what the unit name should be.

I think ffr would be better. It means "forced fraction".

You are forcing it to take the fraction size and ignore the content size. So a "forced" version of the fr unit makes more sense to me than efr (aka "equal fraction). "Equal fraction" makes me think "what is it equal to?".

Also ffr is easier to type than efr.

[Loirooriol]

Your problem is not with the fr unit, it's with the default min track sizing function.
So adding a new unit seems like a wrong solution to me.