test262 has an awesome new feature that allows dynamically selecting test chapters to run. It appears to be pulling in the number of tests per chapter by loading the ch*.json files which includes the tests themselves. From the east coast of the US, it takes quite some time to download these files (up to 11 megs each) from Mozilla's servers.
A quick performance fix would be to simply load the testcases_ch*.json files (that live alongside the ch*.json files) which include the number of test cases per chapter. These files are only about 46KB apiece.
Keep up the good work!