Some patterns that were valid with /u are invalid with /v.
This CL adds a UseCounter for such usages in /u to get an idea how often
they are used in the wild.
This is important information w.r.t the proposal to use /v instead of /u
for the pattern attribute (http://go/gh/whatwg/html/pull/7908).
Chromium CL: https://crrev.com/c/4221395
Bug: v8:11935
Change-Id: Idc023ceba9ce03eee578d6c387ce8a8f37db292f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4212393
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Jakob Linke <jgruber@chromium.org>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Patrick Thier <pthier@chromium.org>
Cr-Commit-Position: refs/heads/main@{#85639}
5080c7727a