possible fix for checked attribute

html.js.patch

diff --git a/lib/jsdom/level2/html.js b/lib/jsdom/level2/html.js
index 6d92a8f..ae7e38a 100644
--- a/lib/jsdom/level2/html.js
+++ b/lib/jsdom/level2/html.js
@@ -848,11 +848,14 @@ define('HTMLInputElement', {
       return this._initDefaultChecked();
     },
     get checked() {
-      return !!this.getAttribute('checked');
+      return !!this._attributes.getNamedItem('checked');
     },
     set checked(checked) {
       this._initDefaultChecked();
-      this.setAttribute('checked', checked);
+      if (checked)
+          this.setAttribute('checked', 'checked');
+      else
+          this.removeAttribute('checked');
     },
     get value() {
       return this.getAttribute('value');