Fix a misparse when a calc() starts with a non-paren block.
This would cause either a DCHECK or broken error recovery.
Fixed: 367166498
Change-Id: I853a5041f6542ace4a5f031ec9d69b7c47b44005
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5868092
Reviewed-by: Anders Hartvoll Ruud andruud@chromium.org
Commit-Queue: Steinar H Gunderson sesse@chromium.org
Cr-Commit-Position: refs/heads/main@{#1356378}