Support GZip encoding on the http server.

sdk/lib/io/io_sink.dart

 // Copyright (c) 2013, 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.
 
 part of dart.io;
 
 /**
  * Helper class to wrap a [StreamConsumer<List<int>, T>] and provide
  * utility functions for writing to the StreamConsumer directly. The
  * [IOSink] buffers the input given by [write], [writeAll], [writeln],
@@ skipping 119 matching lines @@
 
   void close() {
     if (_isBound) {
       throw new StateError("IOSink is already bound to a stream");
     }
     _controller.close();
   }
 
   Future<T> get done {
     _controller;
-    return _pipeFuture.then((_) => this);
+    return _pipeFuture;
   }
 
   void _completeWriteStreamCompleter([error]) {
     if (_writeStreamCompleter == null) return;
     var tmp = _writeStreamCompleter;
     _writeStreamCompleter = null;
     if (error == null) {
       _bindSubscription = null;
       tmp.complete();
     } else {
       tmp.completeError(error);
     }
   }
 
   StreamController<List<int>> get _controller {
     if (_controllerInstance == null) {
       _controllerInstance = new StreamController<List<int>>(
           onPauseStateChange: _onPauseStateChange,
           onSubscriptionStateChange: _onSubscriptionStateChange);
       var future = _controller.stream.pipe(_target);
       future.then((_) => _completeWriteStreamCompleter(),
                   onError: (error) => _completeWriteStreamCompleter(error));
-      _pipeFuture = future.then((_) => this);
+      _pipeFuture = future.then((value) => value);
     }
     return _controllerInstance;
   }
 
   bool get _isBound => _bindSubscription != null;
 
   void _onPauseStateChange() {
     _paused = _controller.isPaused;
     if (_controller.isPaused) {
       _pause();
@@ skipping 47 matching lines @@
             _completeWriteStreamCompleter();
           } else {
             _controller.close();
           }
         },
         onError: _controller.addError);
     if (_paused) _pause();
     if (unbind) {
       return _writeStreamCompleter.future;
     } else {
-      return _pipeFuture.then((_) => this);
+      return _pipeFuture;
     }
   }
 }