Issue 12694. Fix for parsing 'buildIn() {}' top-level functions.

tests/language/built_in_identifier_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Check that we can use pseudo keywords as names in function level code.
 
 import "package:expect/expect.dart";
 
 
 class PseudoKWTest {
   static testMain() {
@@ skipping 20 matching lines @@
     // "native" is a per-implementation extension that is not a part of the
     // Dart language.  While it is not an official built-in identifier, it
     // is useful to ensure that it remains a legal identifier.
     var native = 0;
 
 
     // The code below adds a few additional variants of usage without any
     // attempt at complete coverage.
     {
       void factory(set) {
-        return 0;  /// 01: ok
+        return;  /// 01: ok
       }
     }
 
     get: while (import > 0) {
       break get;
     }
 
     return
         static +  /// 01: ok
         library * operator;
@@ skipping 55 matching lines @@
   Expect.equals(1, A.static());  /// 01: ok
   typedef("T");  /// 01: ok
   Expect.equals("typedef T", typedef("T"));  /// 01: ok
   static("true");  /// 01: ok
   Expect.equals(false, static("true"));  /// 01: ok
   Expect.equals(5, C.operator);
   Expect.equals(null, C.get);
   C.set = 0;
   Expect.equals(111, C.set);
 }