8031359: Invocable.getInterface() works incorrectly if interface has default methods
Reviewed-by: attila, hannesw
x instanceof f: true
x instanceof b: true
y instanceof f: true
y instanceof b: true
Changing prototype
x instanceof f: false
x instanceof b: false
y instanceof f: false
y instanceof b: false
Bound function prototype
f.hasOwnProperty('prototype'): true
b.hasOwnProperty('prototype'): false