Patcher: remove wrappers when window is closed to avoid memory leaks

[Infocatcher]

Seems like garbage collector can't cleanup links to global extension object after window will be closed.

[Infocatcher]

Testcase:

var count = 25;
function leakTestPrototype() {
    for(var i = 1; i <= count; ++i) {
        var win = window.openDialog(location.href, "", "chrome,all");
        win.addEventListener("load", function loader(e) {
            win.document.documentElement.setAttribute("titlemodifier_normal", "[" + i + "/" + count + "]");
            win.removeEventListener(e.type, loader, false);
            win.setTimeout(function() {
                win.close();
                leakTestPrototype.__gen.next();
            }, 500);
        }, false);
        yield;
    }
    yield;
}
var leakTest = leakTestPrototype.__gen = leakTestPrototype();
leakTest.next();

• open new window and close it
• disable extension
• open about:memory?verbose, run "Minimize memory usage" and refresh page
• search for "privateTab" – shouldn't be found

[Infocatcher]

Looks fixed for me.
Tested on Firefox 20.0.1 and 23.0a1 (2013-04-25).

But there is another possible (and known) issue: if patcher unable to restore original function (in case of patches from third-party extensions), wrapper will not be completely removed to preserve functionality (but not memory).