https://w3c.github.io/webappsec-csp/#directive-report-to

The directive value of "report-to" is a single token according to the spec, but Blink implementation handles it as if ascii-whitespace-delimited list of tokens.

Found during code investigation for another purpose.
https://chromium-review.googlesource.com/c/chromium/src/+/1379321
Probably the priority is quite low.