[css-grid-1] Browsers disagree on layout of all-auto columns with overlapping spans

[tabatkins]

In #2356, Florian provides an example layout using a bunch of fixed-size items spanning 5 auto columns in various configutations https://unicode.org/cldr/utility/. Firefox and Chrome give similar results, but not identical; Edge gives a dramatically different result:

• In Firefox, the grid as a whole is 745x590, with extra horizontal space on items 1, 2, 4, 7, and 8.
• In Chrome, the grid as a whole is 760x590, with extra horizontal space on items 2, 4, 6, 7, and 8.
• In Edge, the grid as a whole is 760x710, with extra vertical space on items 1, 3, 5, and 6. (Note: to get a reasonable display you'll need to float: left the grid, as Edge doesn't yet support width: max-content.)

This is all very confusing and distressing! Who's right, if any? What needs to be fixed in the spec to make this clearer?

/cc @mrego @MatsPalmgren @atanassov

[MatsPalmgren]

Firefox Nightly and Chrome Canary (both on Linux) have identical layout AFAICT.
The content area is 750x580 and the used track sizes are the same in both:

grid-template-columns: 160px 140px 125px 75px 210px;
grid-template-rows: 260px 90px 100px 100px;

We fixed a sizing bug for spanning items somewhat recently (caused by Grid spec bug #1729, fwiw). It'll be in the next release (v60). That might explain your different results if you were testing v59.
(FYI, v60 is planned to be released 2018-05-09)

[tabatkins]

Hahaha, I'm actually on Firefox 52, because that's the ESR installed by Ubuntu's apt-get. ://///

But if Firefox is matching Chrome now, that's 👍. It's just Edge's behavior that is somewhat boggling, then.

[MatsPalmgren]

On Ubuntu 17.10 I get FF59 when I do "apt-get install firefox". I'm guessing you're using an Ubuntu LTS or something? Anyway, I'd recommend always testing Nightly for stuff like this.