[PEPC] Don't apply border-radius restrictions if it's a single value

With a single value border-radius will usually create a pill-shape.
However with the min restrictions the permission element applies, this
behavior is lost. Since this is desired behavior by developers and the
reason why the border-radius restrictions were added is entirely
different, this CL does not apply the restrictions if all the radii are
identical.

Fixed: 450226375
Change-Id: If737fb3cf962a87e4661d042604e072e7f990f8a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7021635
Reviewed-by: Anders Hartvoll Ruud <andruud@chromium.org>
Commit-Queue: Andy Paicu <andypaicu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1527392}