Introduce support for ExtendedAttributeIdentList in the IDL parser.

tools/idl_parser/test_parser/interface_web.idl

Index: tools/idl_parser/test_parser/interface_web.idl
diff --git a/tools/idl_parser/test_parser/interface_web.idl b/tools/idl_parser/test_parser/interface_web.idl
index da1dfcdaace07ca6c4a544c8aac9dacdb89d74c8..8d41e91f82ccc7b51eaee72d5ccba87d28abd3dd 100644
--- a/tools/idl_parser/test_parser/interface_web.idl
+++ b/tools/idl_parser/test_parser/interface_web.idl
@@ -162,3 +162,22 @@ interface MyIFaceStringifiers {
   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();
+};