Update dart2js unit tests to new library API.

dart/tests/utils/dummy_compiler_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.
 
 // Smoke test of the dart2js compiler API.
+library dummy_compiler;
 
 import 'dart:async';
-library dummy_compiler;
+import 'dart:uri';
 
 import '../../sdk/lib/_internal/compiler/compiler.dart';
-import 'dart:uri';
 
 Future<String> provider(Uri uri) {
   Completer<String> completer = new Completer<String>();
   String source;
   if (uri.scheme == "main") {
     source = "main() {}";
   } else if (uri.scheme == "lib") {
     if (uri.path.endsWith("/core.dart")) {
       source = """library core;
                   class Object {}
@@ skipping 50 matching lines @@
 
 main() {
   String code = compile(new Uri.fromComponents(scheme: 'main'),
                         new Uri.fromComponents(scheme: 'lib', path: '/'),
                         new Uri.fromComponents(scheme: 'package', path: '/'),
                         provider, handler).value;
   if (code == null) {
     throw 'Compilation failed';
   }
 }