Regression test for keyboard layout fingerprinting in KeyboardEvent fails

The test in dom/events/test/test_tor_bug15646.html fails with the following error:

53 INFO TEST-UNEXPECTED-FAIL | dom/events/test/test_tor_bug15646.html | uncaught exception - ReferenceError: spawnTask is not defined at http://mochi.test:8888/tests/dom/events/test/test_tor_bug15646.html:127