Reviewed-by: alanb

Reviewed-by: kcr, mchung, alanb

Summary: Before computing intersection of thrown types, javac must make sure type variables come from the same set.
Reviewed-by: mcimadamore

Reviewed-by: attila, mhaupt

Reviewed-by: ihse

Reviewed-by: tbell

Reviewed-by: ctornqvi, amurillo

Reviewed-by: jjg

Reviewed-by: jjg

Reviewed-by: hseigel, gtriantafill