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

sdk/lib/io/socket_stream_impl.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.
 
 class _SocketInputStream implements InputStream {
   _SocketInputStream(Socket socket) : _socket = socket {
     if (_socket._closed) _closed = true;
     _socket.onClosed = _onClosed;
   }
 
   List<int> read([int len]) {
     return _socket.read(len);
   }
 
   int readInto(List<int> buffer, [int offset = 0, int len]) {
     if (_closed) return null;
-    if (len === null) len = buffer.length;
+    if (len == null) len = buffer.length;
     if (offset < 0) throw new StreamException("Illegal offset $offset");
     if (len < 0) throw new StreamException("Illegal length $len");
     return _socket.readList(buffer, offset, len);
   }
 
   int available() => _socket.available();
 
   void pipe(OutputStream output, {bool close: true}) {
     _pipe(this, output, close: close);
   }
@@ skipping 14 matching lines @@
     _clientCloseHandler = callback;
     _socket._onClosed = _onClosed;
   }
 
   void set onError(void callback(e)) {
     _onError = callback;
   }
 
   void _onClosed() {
     _closed = true;
-    if (_clientCloseHandler !== null) {
+    if (_clientCloseHandler != null) {
       _clientCloseHandler();
     }
   }
 
   bool _onSocketError(e) {
     close();
     if (_onError != null) {
       _onError(e);
       return true;
     } else {
@@ skipping 135 matching lines @@
     }
   }
 
   Socket _socket;
   _BufferList _pendingWrites;
   Function _onNoPendingWrites;
   Function _onClosed;
   bool _closing = false;
   bool _closed = false;
 }