This test checks whether event handlers for outstanding XMLHttpRequests survive garbage collection.

See https://bugs.webkit.org/show_bug.cgi?id=9113 REGRESSION (14581): XMLHttpRequest never calls onreadystatechange with a readystate == 4

If the test passes, you'll see a series of 'PASS' messages below.

PASS: event handler fired, readyState: 1.
PASS: event handler fired after garbage collection, readyState: 2.
PASS: event handler fired after garbage collection, readyState: 3.
PASS: event handler fired after garbage collection, readyState: 4.