bindings: Fixes layouttests when moving attributes to prototype chains.

LayoutTests/resources/js-test.js

Index: LayoutTests/resources/js-test.js
diff --git a/LayoutTests/resources/js-test.js b/LayoutTests/resources/js-test.js
index 10abf0bc336b48f85c4658e6af7efd4818a7443b..2a926bbc45cf838ad509bdcb8f88e044cf4d8788 100644
--- a/LayoutTests/resources/js-test.js
+++ b/LayoutTests/resources/js-test.js
@@ -199,6 +199,18 @@ function stringify(v)
     else return "" + v;
 }
 
+// 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(domObject)
+{
+    var object = {};
+    for (var property in domObject) {
+        object[property] = domObject[property];
+    }
+    return JSON.stringify(object);
+}
+
 function evalAndLog(_a, _quiet)
 {
   if (typeof _a != "string")