Mutates in place: the message was decoded from the wire moments ago and has
no other owner, and a copy per frame would give back what the elision saved.
A frame without the header is left entirely alone, which is what makes this
safe to run unconditionally on every inbound message.
Put back the mimetypes elideStickyMetadata left out.
Mutates in place: the message was decoded from the wire moments ago and has no other owner, and a copy per frame would give back what the elision saved. A frame without the header is left entirely alone, which is what makes this safe to run unconditionally on every inbound message.