Scope extensions explainer: consider using URLPattern syntax for include and exclude paths

[LuHuangMSFT]

See: https://github.com/WICG/urlpattern/blob/main/mdn-drafts/QUICK-REFERENCE.md
URLPattern allows per-path-element pattern matching and other useful syntax.

[kenchris]

@wanderview fyi

[LuHuangMSFT]

Discussions with @alancutter and @wanderview identified these concerns:

1. Performance of URLPattern matching on different platforms. Computation requirement could make this usage impractical on some platforms. One approach here is to use a subset of the URLPattern syntax in exchange for better performance characteristics.
2. OS integration in the future - using a more complicated syntax to define scope could make it difficult or impossible translate that scope to OS-specific APIs (such as the ones for registering protocol or link handling).

I expect that that finding a well-rounded solution to these problems will take some time. We will structure scope_extension JSON format to accept improvements in the future.

[wanderview]

Hmm, I don't recall discussing performance concerns. What I've measured so far is in the single digit microseconds in the lab, so I wouldn't expect a huge performance impact.

The OS integration issue I believe was regarding android intent integration which would have difficulty completely matching full URLPattern features. I thought, however, @alancutter was of the opinion we should not target the lowest common denominator.

Anyway, just wanted to clarify my position.

[alancutter]

We should not target only the lowest common denominator but we should allow for it to be catered to by sites.
I would like to see a pattern akin to display_override where multiple entries can be specified and the user agent will pick the first that it can support.

Sketch:

{
  paths: [{
    mode: 'pattern',
    include_patterns: [ ... ],
    exclude_patterns: [ ... ],
  }, {
    mode: 'path',
    include_paths: [ ... ],
    exclude_paths: [ ... ],
  }, {
    mode: 'path',
    include_path: [ ... ],
    // Some platforms don't support path exclusion.
  }],
}