1 Test that WebKitMutationObserver.disconnect cancels pending delivery
3 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
6 Disconnecting should cancel any pending delivery...
8 ...and re-observing should not see any of the previously-generated records.
9 PASS mutations.length is 1
10 PASS mutations[0].attributeName is "bar"
11 PASS successfullyParsed is true