8023368: Instance __proto__ property should exist and be writable.
Reviewed-by: attila, hannesw
Compiled OK: box2d
Compiled OK: code-load
Compiled OK: crypto
Compiled OK: deltablue
Compiled OK: earley-boyer
Compiled OK: gbemu
Compiled OK: mandreel
Compiled OK: navier-stokes
Compiled OK: pdfjs
Compiled OK: raytrace
Compiled OK: regexp
Compiled OK: richards
Compiled OK: splay