Minimal fix to get cross frame tests working.

lib/dom/templates/html/frog/impl_IFrameElement.darttemplate

Index: lib/dom/templates/html/frog/impl_IFrameElement.darttemplate
diff --git a/lib/dom/templates/html/frog/impl_IFrameElement.darttemplate b/lib/dom/templates/html/frog/impl_IFrameElement.darttemplate
new file mode 100644
index 0000000000000000000000000000000000000000..204154d30fae31d09d13016b5d7e8f8b819afee4
--- /dev/null
+++ b/lib/dom/templates/html/frog/impl_IFrameElement.darttemplate
@@ -0,0 +1,14 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
+$!MEMBERS
+
+  Window get _contentWindow() native "return this.contentWindow;";
+
+  // Override contentWindow to return secure wrapper.
+  Window get contentWindow() {
+    return _DOMWindowCrossFrameImpl._createSafe(_contentWindow);
+  }
+}