RFR: 8345188: Support tree-structural pseudo-classes [v6]

[Andy Goryachev]

On Wed, 8 Jan 2025 22:12:32 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> Maybe we should deprecate the non-standard `.root` class and mention that in the cssref?
>
> I only pointed this out as I didn't see removal of the old `.root` code, in which case it should either still be documented or mentioned that it will be removed in the future.  I can go with either solution.

Even if it is deprecated for removal, it won't be an instantaneous event.  We still need to document that, and even go further and add a warning that it will be removed, to make sure all the developers have updated their stylesheets.

It probably makes more sense just to keep it, for backward compatibility.

I don't think we want some banking application to go haywire when the selector gets removed.  There is a value in backward compatibility.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1652#discussion_r1907931566