Set only on the compose:email over-length fallback: whether the draft body is now on the
user's clipboard. The copy overwrites whatever the user had copied, so the host must say it
happened, and must not claim it when this is false (no body, clipboard unavailable over plain
HTTP, or denied by permissions policy).
Set only on the compose:email over-length fallback: whether the draft body is now on the user's clipboard. The copy overwrites whatever the user had copied, so the host must say it happened, and must not claim it when this is false (no body, clipboard unavailable over plain HTTP, or denied by permissions policy).