Fix attr() test for custom properties
"elem.style[propertyName]" doesn't work for custom properties, replaced
it with "setProperty()".
Removed leading whitespace before .
Bug: 40320391
Change-Id: Ia2dd6afc44a4449abc17fe77d496d7501538fb3e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5776845
Reviewed-by: Anders Hartvoll Ruud andruud@chromium.org
Commit-Queue: Munira Tursunova moonira@google.com
Cr-Commit-Position: refs/heads/main@{#1340901}