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

runtime/lib/isolate_patch.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.
 
 patch class _ReceivePortFactory {
   /* patch */ factory ReceivePort() {
     return new _ReceivePortImpl();
   }
 }
 
 class _ReceivePortImpl implements ReceivePort {
   factory _ReceivePortImpl() native "ReceivePortImpl_factory";
 
   receive(void onMessage(var message, SendPort replyTo)) {
     _onMessage = onMessage;
   }
 
   close() {
     _portMap.remove(_id);
     _closeInternal(_id);
   }
 
   SendPort toSendPort() {
     return new _SendPortImpl(_id);
   }
 
   /**** Internal implementation details ****/
   // Called from the VM to create a new ReceivePort instance.
   static _ReceivePortImpl _get_or_create(int id) {
-    if (_portMap !== null) {
+    if (_portMap != null) {
       _ReceivePortImpl port = _portMap[id];
-      if (port !== null) {
+      if (port != null) {
         return port;
       }
     }
     return new _ReceivePortImpl._internal(id);
   }
   _ReceivePortImpl._internal(int id) : _id = id {
-    if (_portMap === null) {
+    if (_portMap == null) {
       _portMap = new Map();
     }
     _portMap[id] = this;
   }
 
   // Called from the VM to dispatch to the handler.
   static void _handleMessage(int id, int replyId, var message) {
-    assert(_portMap !== null);
+    assert(_portMap != null);
     ReceivePort port = _portMap[id];
     SendPort replyTo = (replyId == 0) ? null : new _SendPortImpl(replyId);
     (port._onMessage)(message, replyTo);
   }
 
   // Call into the VM to close the VM maintained mappings.
   static _closeInternal(int id) native "ReceivePortImpl_closeInternal";
 
   final int _id;
   var _onMessage;
 
   // id to ReceivePort mapping.
   static Map _portMap;
 }
 
 
 class _SendPortImpl implements SendPort {
   /*--- public interface ---*/
   void send(var message, [SendPort replyTo = null]) {
     this._sendNow(message, replyTo);
   }
 
   void _sendNow(var message, SendPort replyTo) {
-    int replyId = (replyTo === null) ? 0 : replyTo._id;
+    int replyId = (replyTo == null) ? 0 : replyTo._id;
     _sendInternal(_id, replyId, message);
   }
 
   Future call(var message) {
     final completer = new Completer();
     final port = new _ReceivePortImpl();
     send(message, port.toSendPort());
     port.receive((value, ignoreReplyTo) {
       port.close();
       if (value is Exception) {
@@ skipping 28 matching lines @@
       native "SendPortImpl_sendInternal_";
 
   final int _id;
 }
 
 _getPortInternal() native "isolate_getPortInternal";
 
 ReceivePort _portInternal;
 
 patch ReceivePort get port {
-  if (_portInternal === null) {
+  if (_portInternal == null) {
     _portInternal = _getPortInternal();
   }
   return _portInternal;
 }
 
 patch spawnFunction(void topLevelFunction()) native "isolate_spawnFunction";
 
 patch spawnUri(String uri) native "isolate_spawnUri";