Calling point:

Our CSP trait that needs a new method to delegate:
Relevant spec: https://www.w3.org/TR/CSP3/#directive-base-uri

Since the CSP code lives in a separate crate (https://github.com/rust-ammonia/rust-content-security-policy) which has the relevant implementation: https://github.com/rust-ammonia/rust-content-security-policy/blob/90a0221fa0b1834c7072da4f690326c420e9b397/src/lib.rs#L341 we need to delegate to it like we do with the other trait implementations

Testing: ./mach test-wpt /content-security-policy/base-uri