Big merge from experimental to bleeding edge.

pkg/http/lib/src/io_client.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.
 
 library io_client;
 
+import 'dart:async';
 import 'dart:io';
 
 import 'base_client.dart';
 import 'base_request.dart';
 import 'streamed_response.dart';
 import 'utils.dart';
 
 /// A `dart:io`-based HTTP client. This is the default client.
 class IOClient extends BaseClient {
   /// The underlying `dart:io` HTTP client.
   HttpClient _inner;
 
   /// Creates a new HTTP client.
   IOClient() : _inner = new HttpClient();
 
   /// Sends an HTTP request and asynchronously returns the response.
   Future<StreamedResponse> send(BaseRequest request) {
     var stream = request.finalize();
 
     var completer = new Completer<StreamedResponse>();
     var connection = _inner.openUrl(request.method, request.url);
+    bool completed = false;
     connection.followRedirects = request.followRedirects;
     connection.maxRedirects = request.maxRedirects;
     connection.onError = (e) {
       async.then((_) {
         // TODO(nweiz): issue 4974 means that any errors that appear in the
         // onRequest or onResponse callbacks get passed to onError. If the
         // completer has already fired, we want to re-throw those exceptions
         // to the top level so that they aren't silently ignored.
-        if (completer.future.isComplete) throw e;
+        if (completed) throw e;
 
-        completer.completeException(e);
+        completed = true;
+        completer.completeError(e);
       });
     };
 
     connection.onRequest = (underlyingRequest) {
       underlyingRequest.contentLength = request.contentLength;
       underlyingRequest.persistentConnection = request.persistentConnection;
       request.headers.forEach((name, value) {
         underlyingRequest.headers.set(name, value);
       });
 
       if (stream.closed) {
         underlyingRequest.outputStream.close();
       } else {
         stream.pipe(underlyingRequest.outputStream);
       }
     };
 
     connection.onResponse = (response) {
       var headers = <String>{};
       response.headers.forEach((key, value) => headers[key] = value);
 
+      if (completed) return;
+
+      completed = true;
       completer.complete(new StreamedResponse(
           response.inputStream,
           response.statusCode,
           response.contentLength,
           request: request,
           headers: headers,
           isRedirect: response.isRedirect,
           persistentConnection: response.persistentConnection,
           reasonPhrase: response.reasonPhrase));
     };
 
     return completer.future;
   }
 
   /// Closes the client. This terminates all active connections. If a client
   /// remains unclosed, the Dart process may not terminate.
   void close() {
     if (_inner != null) _inner.shutdown(force: true);
     _inner = null;
   }
 }