MOD throw errors at event listeners,
allow for to debug event handlers.
ADD ability for receiver only legacyWindows
MOD loose class check at WindowProxyDispatcher.findWindowProxyObjectInWindow
Enable to manually instantiate WindowProxyLegacy or WindowProxyHTML5 instead of WindowProxy
ADD IE8 support for postMessage,
NOTE only frames,iframes are supported, no windows but this is better than legacy
Document receiver only windows