Support dimension type for attr()
We use CSS syntax parser to parse attribute type, but is not
part of CSSSyntaxDefinition, so we need to handle them separately.
Bug: 40320391
Change-Id: Idf8722f543240b005749b819caa2b134124a2ff0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5683583
Commit-Queue: Munira Tursunova moonira@google.com
Reviewed-by: Anders Hartvoll Ruud andruud@chromium.org
Cr-Commit-Position: refs/heads/main@{#1336684}