[css-color-4] Preserve token range on malformed color-mix/color-contrast

Otherwise we get into problems with double-bar grammars, like e.g.
'border:1px solid color-mix(gibberish)', which will parse successfully
as 'border:1px solid' because the range is left AtEnd in error cases.

Fixed: 1442130
Change-Id: I0d4495afa4cde77d30e88c22c998a4091ce6d56e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4507075


Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Auto-Submit: Anders Hartvoll Ruud <andruud@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1140099}