Add new argument to compiler.

tests/compiler/dart2js/package_root_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 that the compiler can handle imports when package root has not been set.
 
 library dart2js.test.package_root;
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
@@ skipping 39 matching lines @@
   EventSink<String> outputProvider(String name, String extension) {
     if (name != '') throw 'Attempt to output file "$name.$extension"';
     return new NullSink('$name.$extension');
   }
 
   Compiler compiler = new Compiler(provider,
                                    outputProvider,
                                    diagnosticHandler,
                                    libraryRoot,
                                    null,
-                                   []);
+                                   [],
+                                   {});
 
   asyncTest(() => compiler.run(main).then((_) {
     Expect.equals(1, errors.length);
     Expect.equals("Error: Cannot resolve 'package:foo/foo.dart'. "
                   "Package root has not been set.",
                   errors[0]);
   }));
 }
 
 void main() {
   runCompiler(Uri.parse('memory:main.dart'));
   runCompiler(Uri.parse('package:foo/foo.dart'));
 }