Use strict equality when comparing with null, especially when null is a default value.

runtime/bin/socket_impl.dart

 // Copyright (c) 2011, 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.
 
 
 class _SocketBase {
 
   /*
    * Keep these constants in sync with the native poll event identifiers.
    */
@@ skipping 63 matching lines @@
     if (_canActivateHandlers && (_id >= 0)) {
       EventHandler._sendData(_id, _handler, _handlerMask);
     }
   }
 
   void _scheduleEvent(int event) {
     _handler.toSendPort().send([1 << event], null);
   }
 
   int get port() {
-    if (_port == null) {
+    if (_port === null) {
       _port = _getPort();
     }
     return _port;
   }
 
   void close() {
     if (_id >= 0) {
       EventHandler._sendData(_id, _handler, 1 << _CLOSE_COMMAND);
       _handler.close();
       _handler = null;
       _id = -1;
     } else {
       // This is to support closing sockets created but never assigned
       // any actual socket.
-      if (_handler == null) {
+      if (_handler === null) {
         throw new
             SocketIOException("Error: close failed - invalid socket handle");
       } else {
         _handler.close();
         _handler = null;
       }
     }
   }
 
 
@@ skipping 159 matching lines @@
 
   void setDataHandler(void callback()) {
     _setHandler(_IN_EVENT, callback);
   }
 
   void setCloseHandler(void callback()) {
     _setHandler(_CLOSE_EVENT, callback);
   }
 
   InputStream get inputStream() {
-    if (_inputStream == null) {
+    if (_inputStream === null) {
       _inputStream = new SocketInputStream(this);
     }
     return _inputStream;
   }
 
   OutputStream get outputStream() {
-    if (_outputStream == null) {
+    if (_outputStream === null) {
       _outputStream = new SocketOutputStream(this);
     }
     return _outputStream;
   }
 
   SocketInputStream _inputStream;
   SocketOutputStream _outputStream;
 }