[css-typed-om] Avoid infinite recursion when serializing CSSUnparsedValue
It's possible to create cyclic CSSUnparsedValues. This causes infinite
recursion when serializing the value. The spec needs to say how this
should be handled, but meanwhile, we handle the problem by serializing
an empty string for cycles.
Fixed: 371292572
Change-Id: I15ff38ff2b87eecec1f175d6aab7736dcf8091ed
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5905363
Reviewed-by: Rune Lillesveen futhark@chromium.org
Commit-Queue: Anders Hartvoll Ruud andruud@chromium.org
Cr-Commit-Position: refs/heads/main@{#1365367}