Add a web socket client

runtime/bin/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 SocketInputStream {
   _SocketInputStream(Socket socket) : _socket = socket {
     if (_socket._id == -1) _closed = true;
     _socket.onClosed = _onClosed;
   }
 
@@ skipping 94 matching lines @@
 
   bool writeFrom(List<int> buffer, [int offset = 0, int len]) {
     return _write(
         buffer, offset, (len == null) ? buffer.length - offset : len, true);
   }
 
   void close() {
     if (!_pendingWrites.isEmpty()) {
       // Mark the socket for close when all data is written.
       _closing = true;
-      _socket._onWrite = _onWrite;
+      _setupWriteHander();
     } else {
       // Close the socket for writing.
       _socket._closeWrite();
       _closed = true;
     }
   }
 
   void destroy() {
     _socket.onWrite = null;
     _pendingWrites.clear();
     _socket.close();
     _closed = true;
   }
 
   void set onNoPendingWrites(void callback()) {
+    if (_noPendingWritesTimer != null) {
+      _noPendingWritesTimer.cancel();
+      _noPendingWritesTimer = null;
+    }
     _onNoPendingWrites = callback;
     if (_onNoPendingWrites != null) {
-      _socket._onWrite = _onWrite;
+      if (_pendingWrites.isEmpty()) {
+        _noPendingWritesTimer = new Timer(0, (t) {
+          if (_onNoPendingWrites != null) _onNoPendingWrites();
+        });
+      } else {
+        _setupWriteHander();
+      }
     }
   }
 
   bool _write(List<int> buffer, int offset, int len, bool copyBuffer) {
     if (_closing || _closed) throw new StreamException("Stream closed");
     int bytesWritten = 0;
     if (_pendingWrites.isEmpty()) {
       // If nothing is buffered write as much as possible and buffer
       // the rest.
       bytesWritten = _socket.writeList(buffer, offset, len);
       if (bytesWritten == len) return true;
     }
 
     // Place remaining data on the pending writes queue.
     int notWrittenOffset = offset + bytesWritten;
     if (copyBuffer) {
       List<int> newBuffer =
           buffer.getRange(notWrittenOffset, len - bytesWritten);
       _pendingWrites.add(newBuffer);
     } else {
       assert(offset + len == buffer.length);
       _pendingWrites.add(buffer, notWrittenOffset);
     }
-    _socket._onWrite = _onWrite;
+    _setupWriteHander();
     return false;
   }
 
   void _onWrite() {
     // Write as much buffered data to the socket as possible.
     while (!_pendingWrites.isEmpty()) {
       List<int> buffer = _pendingWrites.first;
       int offset = _pendingWrites.index;
       int bytesToWrite = buffer.length - offset;
       int bytesWritten = _socket.writeList(buffer, offset, bytesToWrite);
@@ skipping 11 matching lines @@
     } else {
       if (_onNoPendingWrites != null) _onNoPendingWrites();
     }
     if (_onNoPendingWrites == null) {
       _socket._onWrite = null;
     } else {
       _socket._onWrite = _onWrite;
     }
   }
 
+  void _setupWriteHander() {
+    // Set up the callback for writing the pending data as the
+    // underlying socket becomes ready for writing.
+    if (_noPendingWritesTimer != null) {
+      _noPendingWritesTimer.cancel();
+      _noPendingWritesTimer = null;
+    }
+    _socket._onWrite = _onWrite;
+  }
+
   bool _onSocketError(e) {
     close();
     if (_onError != null) {
       _onError(e);
       return true;
     } else {
       return false;
     }
   }
 
   Socket _socket;
   _BufferList _pendingWrites;
-  var _onNoPendingWrites;
+  Function _onNoPendingWrites;
+  Timer _noPendingWritesTimer;
   bool _closing = false;
   bool _closed = false;
 }