Support for CSS :link selector

[frewsxcv]

https://html.spec.whatwg.org/multipage/#selector-link

https://drafts.csswg.org/selectors/#link

[salty-horse]

Seems implemented here: components/script/dom/element.rs:1680

[SimonSapin]

:link is misnamed in CSS since it’s exclusive with :visited: it only matches links that are not visited. I’ve named the trait methods according to the pseudo-classes’ meaning rather than their syntax:

• Selector :link calls trait method fn is_unvisited_link(&self) -> bool
• Selector :visited calls trait method fn is_visited_link()(&self) -> bool
• Selector :any-link is equivalent to :matches(:link, :visited), calls trait method fn is_link()(&self) -> bool

https://github.com/servo/rust-selectors/blob/74a3ff5228/src/parser.rs#L620-L622
https://github.com/servo/rust-selectors/blob/74a3ff5228/src/matching.rs#L657-L666

:link is already implemented, but at the moment it is identical to :any-link for reasons explained in #8718 (comment).

Closing this issue in favor of #8718, since it’s really the same thing.