Grid: Rename Flex to Fraction

[nicoburns]

Objective

This is to more closely align our naming with the spec:

• Renames MaxTrackSizingFunction::Flex to MaxTrackSizingFunction::Fraction
• Renames flex() helper to fr()
• Creates a new helper function called flex() that resolves to minmax(0px, Nfr)

The unit is called fr in the spec (although it does also talk about "flexible track sizing functions".

The flex() helper is to try to encourage people to use minmax(0px 1fr) - this is much faster than plain 1fr as it doesn't have to do any content sizing. Hopefully the pattern for "4 evenly sized tracks" can be something like:

grid_template_columns: repeat(4, flex(1.0))

although the following would also work and be just as effcient

grid_template_columns: repeat(4, percent(1/4))

Feedback wanted

Does this naming make sense?

EDIT: Would it perhaps be better to leave the naming as it is and create an evenly_sized_tracks(count: u16) helper that directly creates a repeat(4, flex(1.0))?

[alice-i-cecile]

create an evenly_sized_tracks(count: u16) helper that directly creates a repeat(4, flex(1.0))?

I like this naming, but I'd also like this helper method.

[nicoburns]

create an evenly_sized_tracks(count: u16) helper that directly creates a repeat(4, flex(1.0))?

I like this naming, but I'd also like this helper method.

Helper method added :)