Make hasNext a getter instead of a method.

tests/compiler/dart2js/mock_compiler.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.
 
 library mock_compiler;
 
 import 'dart:uri';
 
 import '../../../lib/compiler/compiler.dart' as api;
 import '../../../lib/compiler/implementation/dart2jslib.dart' hide TreeElementMapping;
@@ skipping 184 matching lines @@
     SourceFile sourceFile = sourceFiles[uri.toString()];
     if (sourceFile === null) throw new ArgumentError(uri);
     return new Script(uri, sourceFile);
   }
 }
 
 void compareWarningKinds(String text, expectedWarnings, foundWarnings) {
   var fail = (message) => Expect.fail('$text: $message');
   Iterator<MessageKind> expected = expectedWarnings.iterator();
   Iterator<WarningMessage> found = foundWarnings.iterator();
-  while (expected.hasNext() && found.hasNext()) {
+  while (expected.hasNext && found.hasNext) {
     Expect.equals(expected.next(), found.next().message.kind);
   }
-  if (expected.hasNext()) {
+  if (expected.hasNext) {
     do {
       print('Expected warning "${expected.next()}" did not occur');
-    } while (expected.hasNext());
+    } while (expected.hasNext);
     fail('Too few warnings');
   }
-  if (found.hasNext()) {
+  if (found.hasNext) {
     do {
       print('Additional warning "${found.next()}"');
-    } while (found.hasNext());
+    } while (found.hasNext);
     fail('Too many warnings');
   }
 }
 
 void importLibrary(LibraryElement target, LibraryElement imported,
                    Compiler compiler) {
   for (var element in imported.localMembers) {
     compiler.withCurrentElement(element, () {
       target.addToScope(element, compiler);
     });
   }
 }
 
 LibraryElement mockLibrary(Compiler compiler, String source) {
   Uri uri = new Uri.fromComponents(scheme: "source");
   var library = new LibraryElement(new Script(uri, new MockFile(source)));
   importLibrary(library, compiler.coreLibrary, compiler);
   return library;
 }