Support Promise<T> syntax 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 163 matching lines @@
  *      ExtAttribute(MethodIdentList)
  *  ExtAttributes()
  *    ExtAttribute(MyExtendedAttribute)
  *    ExtAttribute(MyExtendedIdentListAttribute)
  */
 [MyExtendedAttribute,
  MyExtendedIdentListAttribute=(Foo, Bar, Baz)]
 interface MyExtendedAttributeInterface {
   [Attr, MethodIdentList=(Foo, Bar)] void method();
 };
+
+/* TREE
+ *Interface(MyIfacePromise)
+ *  Operation(method1)
+ *    Arguments()
+ *    Type()
+ *      Promise(Promise)
+ *        Type()
+ *          PrimitiveType(void)
+ *  Operation(method2)
+ *    Arguments()
+ *    Type()
+ *      Promise(Promise)
+ *        Type()
+ *          PrimitiveType(long)
+ *  Operation(method3)
+ *    Arguments()
+ *    Type()
+ *      Promise(Promise)
+ *        Type()
+ *          Any()
+ *  Operation(method4)
+ *    Arguments()
+ *    Type()
+ *      Promise(Promise)
+ *        Type()
+ *          Any()
+ */
+interface MyIfacePromise {
+  Promise<void> method1();
+  Promise<long> method2();
+  Promise<any> method3();
+  Promise method4();
+};