This class uses IE's ActiveX "htmlfile" with an embedded iframe to stream events.
http://cometdaily.com/2007/11/18/ie-activexhtmlfile-transport-part-ii/
The main issue with this implementation is that we can't detect initial connection errors. A connection timer is
setup to detect this.
Another issues is that the memory required for the iframe constantly grows so the server occasionally disconnects the
client who then reestablishes the connection with an empty iframe. To alleviate the issue the client removes script
tags as the messages in them have been processed.
The protocol for this transport is a stream of
org.atmosphere.gwt.client.impl.BaseCometTransport