Access Chrome's internal gzip routine from Javascript
If a javascript implementation isn't fast enough for you, you could use native client.
You would use some gzip library in c/c++, and write the glue code so javascript can call it through native client. It should be near or equal to the speed you would get from calling chrome's internal routine were that possible.
Based on this answer to a Stack Overflow question, manually applying gzip to a WebSocket is completely unnecessary. As of version 19, Chrome will apparently compress WebSocket traffic automatically when the server supports it.