Fix XMLHttpRequest leak document when send() is called multiple times.

LayoutTests/fast/dom/resources/leak-check.js

-// include fast/js/resources/js-test-pre.js before this file.
-
-function doLeakTest(src, tolerance) {
-    function getCounterValues() {
-        testRunner.resetTestHelperControllers();
-        gc();
-        return {'numberOfLiveDocuments': window.internals.numberOfLiveDocuments()};
-    }
-
-    var frame = document.createElement('iframe');
-    document.body.appendChild(frame);
-    function loadSourceIntoIframe(src, callback) {
-        var originalSrc = frame.src;
-
-        frame.onload = function() {
-            if (frame.src === originalSrc)
-                return true;
-
-            callback();
-            return true;
-        };
-        frame.src = src;
-    }
-
-    function compareValues(countersBefore, countersAfter, tolerance) {
-        for (type in tolerance) {
-            var before = countersBefore[type];
-            var after = countersAfter[type];
-
-            if(after - before <= tolerance[type])
-                testPassed('The difference of counter "'+type+'" before and after the cycle is under the threshold of '+tolerance[type]+'.');
-            else
-                testFailed('counter "'+type+'" was '+before+' before and now '+after+' after the cycle. This exceeds the threshold of '+tolerance[type]+'.');
-        }
-    }
-
-    jsTestIsAsync = true;
-    if (!window.internals) {
-        debug("This test only runs on DumpRenderTree, as it requires existence of window.internals and cross-domain resource access check disabled.");
-        finishJSTest();
-    }
-
-    loadSourceIntoIframe('about:blank', function() {
-        // blank document loaded...
-        var countersBefore = getCounterValues();
-
-        loadSourceIntoIframe(src, function() {
-            // target document loaded...
-
-            loadSourceIntoIframe('about:blank', function() {
-                // target document unloaded...
-
-                var countersAfter = getCounterValues();
-                compareValues(countersBefore, countersAfter, tolerance);
-                finishJSTest();
-            });
-        });
-    });
-}
-
-function htmlToUrl(html) {
-    return 'data:text/html;charset=utf-8,' + html;
-}
-
-function grabScriptText(id) {
-    return document.getElementById(id).innerText;
-}
-
-// include fast/js/resources/js-test-post.js after this file.