Fix exit_code_test after refactoring.

tests/compiler/dart2js/exit_code_test.dart

 // Copyright (c) 2013, 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 the exit code of dart2js in case of exceptions, errors, warnings, etc.
 
 
 import 'dart:async';
 import 'dart:io' show Platform;
 
@@ skipping 40 matching lines @@
                String this.testType,
                Function this.onTest)
       : super(inputProvider, outputProvider, handler,
             new api.CompilerOptions.parse(
                 libraryRoot: libraryRoot,
                 packageRoot: packageRoot,
                 options: options,
                 environment: environment,
                 packageConfig: packageConfig,
                 packagesDiscoveryProvider: findPackages)) {
-    scanner = new TestScanner(this);
-    resolver = new TestResolver(this, backend.constantCompilerTask);
     reporter = new TestDiagnosticReporter(this, super.reporter);
     test('Compiler');
   }
 
+  @override
+  ScannerTask createScannerTask() => new TestScanner(this);
+
+  @override
+  ResolverTask createResolverTask() {
+    return new TestResolver(this, backend.constantCompilerTask);
+  }
+
   Future<bool> run(Uri uri) {
     test('Compiler.run');
     return super.run(uri);
   }
 
   Future onLibraryScanned(LibraryElement element, LibraryLoader loader) {
     test('Compiler.onLibraryScanned');
     return super.onLibraryScanned(element, loader);
   }
 
@@ skipping 221 matching lines @@
 
       expected = _expectedExitCode(
           beforeRun: tests[marker], fatalWarnings: true);
       totalExpectedErrors += expected.length;
       await testExitCodes(marker, expected, ['--fatal-warnings']);
     }
 
     Expect.equals(totalExpectedErrors, checkedResults);
   });
 }