HTTPS-Only should be disabled for any repeated request caused by a file
drag-and-drop, as HTTPS-Only may block the repeated request if it is insecure,
even if the original request was exempt from HTTPS-Only. Disabling HTTPS-Only
completely is fine in this case, because if we are dragging from an insecure
source, that source must already be exempt from HTTPS-Only, as it otherwise
would have been upgraded already by HTTPS-Only.
The changes in nsContentAreaDragDrop and nsWebBrowserPersist fix this problem on
macOS, the changes in widget/windows/nsDataObj fix it in Windows.
Differential Revision: https://phabricator.services.mozilla.com/D244905
2fa5b90986