Introduce support for ExtendedAttributeIdentList in the IDL parser.

tools/idl_parser/test_parser/interface_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 Interface productions
 
 Run with --test to generate an AST and verify that all comments accurately
 reflect the state of the Nodes.
 
 BUILD Type(Name)
@@ skipping 144 matching lines @@
  *    Attribute(stringValue)
  *      Type()
  *        PrimitiveType(DOMString)
  */
 interface MyIFaceStringifiers {
   stringifier;
   stringifier DOMString ();
   stringifier DOMString namedStringifier();
   stringifier attribute DOMString stringValue;
 };
+
+/* TREE
+ *Interface(MyExtendedAttributeInterface)
+ *  Operation(method)
+ *    Arguments()
+ *    Type()
+ *      PrimitiveType(void)
+ *    ExtAttributes()
+ *      ExtAttribute(Attr)
+ *      ExtAttribute(MethodIdentList)
+ *  ExtAttributes()
+ *    ExtAttribute(MyExtendedAttribute)
+ *    ExtAttribute(MyExtendedIdentListAttribute)
+ */
+[MyExtendedAttribute,
+ MyExtendedIdentListAttribute=(Foo, Bar, Baz)]
+interface MyExtendedAttributeInterface {
+  [Attr, MethodIdentList=(Foo, Bar)] void method();
+};