Support new import rules.

sdk/lib/_internal/compiler/implementation/dart2js.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.
 
 library dart2js.cmdline;
 
 import 'dart:async';
-import 'dart:io';
+import 'dart:io'
+    show exit, File, FileMode, Options, Platform, RandomAccessFile;
 import 'dart:math' as math;
 
 import '../compiler.dart' as api;
 import 'source_file.dart';
 import 'source_file_provider.dart';
 import 'filenames.dart';
 import 'util/uri_extras.dart';
 import 'util/util.dart';
 import '../../libraries.dart';
 
@@ skipping 557 matching lines @@
       }
     } finally {
       exit(253); // 253 is recognized as a crash by our test scripts.
     }
   });
 }
 
 void main() {
   mainWithErrorHandler(new Options());
 }