Unfortunately reverting that causes leaks. Even the "activex" test leaks at least one nsChannel with it reverted.
You will need [my hack attached here](/uploads/4beb8b01bab1de73557b6eac420f150c/leak-tests-hack.diff) to flush all links to be able to test this properly. (this hack is not safe for general use, but it is OK for testing leaks in mshtml tests)