onclose event not raised when websocket is closed

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According to the standard, a browser must send 0xff00 to signal to the remote 
peer that it wants to close the socket. Chrome don't send this chucnk (buggy).
This is why we get 'Disconnected' message from sipML5 when the pending (ghost) 
connection is really closed by the server (e.g. activity) while the current is 
active.
Workaround: check if the closed event is from the active stack

Original issue reported on code.google.com by boss...@yahoo.fr on 29 May 2012 at 5:26