idl_parser: An error should be reduced to DictionaryMembers

tools/idl_parser/test_parser/dictionary_web.idl

 /* Copyright (c) 2013 The Chromium Authors. All rights reserved.
    Use of this source code is governed by a BSD-style license that can be
   found in the LICENSE file. */
 
 /* Test Dictionary productions
 
 Run with --test to generate an AST and verify that all comments accurately
 reflect the state of the Nodes.
 
 BUILD Type(Name)
@@ skipping 66 matching lines @@
  */
 dictionary MyDictRequired {
   required long setLong;
 };
 
 /* ERROR Unexpected "{" after keyword "dictionary". */
 dictionary {
   DOMString? setString = null;
 };
 
+/* TREE
+ *Dictionary(MyDictionaryInvalidOptional)
+ *  Key(mandatory)
+ *    Type()
+ *      PrimitiveType(DOMString)
+ *  Error(Unexpected keyword "optional" after ">".)
+ */
+dictionary MyDictionaryInvalidOptional {
+  DOMString mandatory;
+  sequence<DOMString> optional;
+};
 
 /* ERROR Unexpected identifier "NoColon" after identifier "ForParent". */
 dictionary ForParent NoColon {
   DOMString? setString = null;
 };
 
 /* TREE
  *Dictionary(MyDictNull)
  *  Key(setString)
  *    Type()
  *      PrimitiveType(DOMString)
  *    Default(NULL)
  */
 dictionary MyDictNull {
   DOMString? setString = null;
 };
 
 /* ERROR Unexpected keyword "attribute" after "{". */
 dictionary MyDictUnexpectedAttribute {
   attribute DOMString foo = "";
 };