LearnBoost/socket.io-client — pull request #385 by mixu (2012-02-07 03:13:40+00:00)
Title: Fix XHR.check, which was throwing an error and causing non-IE browsers to fall back to JSONP

There were a few issues with this commit: https://github.com/LearnBoost/socket.io-client/pull/353/files
e.g. socket and socket.options is not defined when called from XHR.xdomainCheck() and http should be a string, not an object.

This meant that the try catch would throw and JSONP would be used for browsers with a working xdomain XHR implementation, which in turn showed as significantly increased CPU usage on clients, particularly FF.