Warn about jQuery.cssNumber

[dmethvin]

See jquery/jquery#4009

Detect assignments to jQuery.cssNumber and recommend that it only be done if that property exists; note that it's going away in 4.0.

Recommend that people do not pass raw numbers to .css() and instead always pass strings and append "px" when appropriate. Point out line-height as a troublesome case.

[dmethvin]

Fixed in aee3d06

[mgol]

@dmethvin Where did that commit land? I don't see it on master... I was about to submit an issue about filling cssNumber and I saw this issue.

[dmethvin]

Darned good question! I can't see it either. I'll reopen this to get it into master.

[dmethvin]

This can't be landed until internal cssNumber usages are removed. I don't think that is going to happen until 4.0.

[mgol]

@dmethvin Oh, I see, the linked commit won't work for jQuery 3.x. That said, it seems we could do something else & detect & warn against pushes to cssNumber? That way Core code would work.

[dmethvin]

Hmmm, sure, we could use a set hook like we did with jQuery.cssProps, I think that should work here as well.