I wonder if browsers can and do re-use the same connection when both domain names resolve to the same IP and both are covered by a single certificate (SAN) when used together on one web site.
Example: I have a certificate covering example.com and example.org in its SubjectAltName. On https://example.com/ I embed images from https://example.org/. Is a (perhaps slow) SSL/TLS handshake for example.org needed?