Make hasNext a getter instead of a method.

tests/compiler/dart2js/pretty_parameter_test.dart

 // Copyright (c) 2011, 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.
 // Test that parameters keep their names in the output.
 
 #import("compiler_helper.dart");
 
 const String FOO = r"""
 void foo(var a, var b) {
 }
@@ skipping 82 matching lines @@
   Expect.isTrue(regexp.hasMatch(generated));
   regexp = const RegExp("bar === true");
   Expect.isTrue(regexp.hasMatch(generated));
 
   generated = compile(MULTIPLE_PHIS_ONE_LOCAL, entry: 'foo');
   regexp = const RegExp(r"var a = 2;");
   Expect.isTrue(regexp.hasMatch(generated));
 
   regexp = const RegExp(r"a = 2;");
   Iterator matches = regexp.allMatches(generated).iterator();
-  Expect.isTrue(matches.hasNext());
+  Expect.isTrue(matches.hasNext);
   matches.next();
-  Expect.isFalse(matches.hasNext());
+  Expect.isFalse(matches.hasNext);
 
   generated = compile(PARAMETER_INIT, entry: 'foo');
   regexp = const RegExp("var result = start;");
   Expect.isTrue(regexp.hasMatch(generated));
 }