bindings: Fixes connect-helper to use stringifyDOMObject.

LayoutTests/http/tests/resources/testharness-helpers.js

 /*
  * testharness-helpers contains various useful extensions to testharness.js to
  * allow them to be used across multiple tests before they have been
  * upstreamed. This file is intended to be usable from both document and worker
  * environments, so code should for example not rely on the DOM.
  */
 
 // Returns a promise that fulfills after the provided |promise| is fulfilled.
 // The |test| succeeds only if |promise| rejects with an exception matching
 // |code|. Accepted values for |code| follow those accepted for assert_throws().
@@ skipping 126 matching lines @@
   assert_true(typeof object === "object", description);
 
   assert_true("hasOwnProperty" in object, description);
 
   // Do not test if |attribute_name| is not an own property because
   // |attribute_name| is in the middle of the transition to a prototype
   // chain.  (http://crbug.com/43394)
 
   assert_true(attribute_name in object, description);
 }
+
+// Stringifies a DOM object.  This function stringifies not only own properties
+// but also DOM attributes which are on a prototype chain.  Note that
+// JSON.stringify only stringifies own properties.
+function stringifyDOMObject(object)
+{
+    function deepCopy(src) {
+        if (typeof src != "object")
+            return src;
+        var dst = Array.isArray(src) ? [] : {};
+        for (var property in src) {
+            dst[property] = deepCopy(src[property]);
+        }
+        return dst;
+    }
+    return JSON.stringify(deepCopy(object));
+}