[@scope] Make prelude selectors unforgiving
The selectors within the @scope prelude were previously unforgiving
(like within :is()), but this was changed in Issue 10042 [1].
Being forgiving means a rule like "@scope (.a, :unknown-thing)"
would behave like "@scope (.a)" (the invalid parts are just silently
ignored), whereas unforgiving behavior would consider it a parse error.
Fixed: 346555843, 343794754
Change-Id: I017c098c1406bcc0df62690038d16879c1e8c110
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5999993
Reviewed-by: Steinar H Gunderson sesse@chromium.org
Commit-Queue: Anders Hartvoll Ruud andruud@chromium.org
Cr-Commit-Position: refs/heads/main@{#1378956}