a === b -> identical(a, b)

sdk/lib/core/options.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.
 
 // Dart core library.
 
 /**
  * The Options object allows accessing the arguments which have been passed to
  * the current isolate.
  */
@@ skipping 27 matching lines @@
    * Returns the path of the script being run in this isolate.
    *
    * If the executable environment does not support [script] an empty
    * string is returned.
    */
   String get script;
 }
 
 class _OptionsImpl implements Options {
   List<String> get arguments {
-    if (_arguments === null) {
+    if (_arguments == null) {
       // On first access make a copy of the native arguments.
       _arguments = _nativeArguments.getRange(0, _nativeArguments.length);
     }
     return _arguments;
   }
 
   String get executable {
     return _nativeExecutable;
   }
 
   String get script {
     return _nativeScript;
   }
 
   List<String> _arguments = null;
 
   // This arguments singleton is written to by the embedder if applicable.
   static List<String> _nativeArguments = const [];
 
   // This executable singleton is written to by the embedder if applicable.
   static String _nativeExecutable = '';
 
   // This script singleton is written to by the embedder if applicable.
   static String _nativeScript = '';
 }