If callee needs to own the param, or if it's making a copy of the param, it's "taking ownership" - even if caller continues to use the original; use pass-by-value.

If caller no longer needs to use the param, it can use std::move with pass-by-value. If callee wants to reduce a copy in the pass-by-value case, it can use std::move.

Why?

See https://chromium-review.googlesource.com/c/chromium/src/+/1099935#message-a0630329edfa4b66e5bea2343a8585235cae8c6b.