URLPattern: Adjust pathname canonicalization based on protocol.

[chromium-wpt-export-bot]

This CL refines the pathname canonicalization routines to account for
differences between "standard" URLs and what chrome calls "path" URLs.
"Path" URLs are referred to as "cannot-be-a-base" URLs in the spec.

To choose the canonicalization routine we look at the protocol pattern
or string. If the protocol matches a "standard" scheme, then we choose
"standard" canonicalization. We also ensure that empty string protocol
values default to "standard" canonicalization. Otherwise we use the
"path" URL canonicalization which is more lenient; e.g. it makes it
easier to write javascript: URL paths, etc.

This CL also exposes two new functions from the url component:

1. GetStandardSchemeList() returns the list of all known standard
   schemes. We need this in order to match them against our protocol
   pattern. For example, http{s}? should match as a standard protocol
   pattern since it matches both http and https. We can't use the
   IsStandard() function for this so we need to expose the whole list to
   iterate and check against.
2. CanonicalizePathURLPath() exposes the per-component canonicalization
   routine for "path" URLs. Previously only a full url parsing function
   was exposed.

Discussed in:

whatwg/urlpattern#33

Bug: 1141510
Change-Id: I3176a36d1e0eb2f8a0ccdf65fde346a4a623f9dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2769358
Commit-Queue: Ben Kelly <wanderview@chromium.org>
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#865276}

[wpt-pr-bot]

The review process for this patch is being conducted in the Chromium project.