[XMLHttpRequest-tests] Fix a bug in overridemimetype-invalid-mime-type.htm (#713)

According to the latest spec, the TypeError should be thrown, not SyntaxError.

Signed-off-by: wanghongjuan <hongjuanx.wang@intel.com>

View on GitHub: https://github.com/w3c/web-platform-tests/pull/713

Received on Tuesday, 4 March 2014 09:41:46 UTC