1895191 - Add a button to select anchor-element in `anchor()` function

Status: NEW

(DevTools :: Inspector: Rules, task)

Description

[Nicolas Chevobbe [:nchevobbe]]

https://drafts.csswg.org/css-anchor-position-1/#anchor-pos

The anchor() function has three arguments:

1. the <anchor-element> value specifies how to find the anchor element it will be drawing positioning information from. If omitted, it behaves as the element’s default anchor specifier. Its possible values are:

• <dashed-ident>: Specifies the anchor name it will look for. This name is a tree-scoped reference.
• implicit: Selects the implicit anchor element defined for the element, if possible.
  See target anchor element for details.

It would be nice if we could display an icon that would highlight the anchor in the page on mouseover, and select it in the markup view when clicked (as we'll do for position-anchor in Bug 1895183)

We may consider adding a InspectorUtils method to retrieve said anchor as it can be non-trivial (see https://drafts.csswg.org/css-anchor-position-1/#target)