Make dartj2s do type conversions on constructor arguments

tools/dom/templates/html/impl/impl_Notification.darttemplate

Index: tools/dom/templates/html/impl/impl_Notification.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_Notification.darttemplate b/tools/dom/templates/html/impl/impl_Notification.darttemplate
index 134f1806cf405d2d592f4fb629c3701f1a4cf106..5a3a5e134d83ad0d852a09dec8d65cd747fe1ab8 100644
--- a/tools/dom/templates/html/impl/impl_Notification.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Notification.darttemplate
@@ -15,13 +15,7 @@ $(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS
     if (lang != null) parsedOptions['lang'] = lang;
     if (tag != null) parsedOptions['tag'] = tag;
     if (icon != null) parsedOptions['icon'] = icon;
-    var nativeOptions;
-$if DART2JS
-    nativeOptions = convertDartToNative_Dictionary(parsedOptions);
-$else
-    nativeOptions = parsedOptions;
-$endif
-    return $CLASSNAME._factory$CLASSNAME(title, nativeOptions);
+    return $CLASSNAME._factory$CLASSNAME(title, parsedOptions);
   }
 $!MEMBERS
 }