Merge all http-outgoing transfomers into _HttpOutgoing, including simpler(better) buffering.

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>>] and provide
  * utility functions for writing to the StreamConsumer directly. The
  * [IOSink] buffers the input given by all [StringSink] methods and will delay
@@ skipping 92 matching lines @@
             _isBound = false;
           });
     }
     if (_controllerInstance == null) return targetAddStream();
     var future = _controllerCompleter.future;
     _controllerInstance.close();
     return future.then((_) => targetAddStream());
   }
 
   Future flush() {
+    if (_isBound) {
+      throw new StateError("StreamSink is bound to a stream");
+    }
+    if (_controllerInstance == null) return new Future.value(this);
     // Adding an empty stream-controller will return a future that will complete
     // when all data is done.
-    var controller = new StreamController()..close();
-    return addStream(controller.stream).then((_) => this);
+    _isBound = true;
+    var future = _controllerCompleter.future;
+    _controllerInstance.close();
+    return future.whenComplete(() {
+          _isBound = false;
+        });
   }
 
   Future close() {
     if (_isBound) {
       throw new StateError("StreamSink is bound to a stream");
     }
     if (!_isClosed) {
       _isClosed = true;
       if (_controllerInstance != null) {
         _controllerInstance.close();
@@ skipping 31 matching lines @@
       throw new StateError("StreamSink is closed");
     }
     if (_controllerInstance == null) {
       _controllerInstance = new StreamController<T>(sync: true);
       _controllerCompleter = new Completer();
       _target.addStream(_controller.stream)
           .then(
               (_) {
                 if (_isBound) {
                   // A new stream takes over - forward values to that stream.
-                  _controllerCompleter.complete();
+                  _controllerCompleter.complete(this);
                   _controllerCompleter = null;
                   _controllerInstance = null;
                 } else {
                   // No new stream, .close was called. Close _target.
                   _closeTarget();
                 }
               },
               onError: (error) {
                 if (_isBound) {
                   // A new stream takes over - forward errors to that stream.
@@ skipping 63 matching lines @@
 
   void writeln([Object obj = ""]) {
     write(obj);
     write("\n");
   }
 
   void writeCharCode(int charCode) {
     write(new String.fromCharCode(charCode));
   }
 }