Refactor http.Client and http.BaseClient to allow http.Client in type annotations.

pkg/http/lib/http.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.
 
 /// A composable, [Future]-based library for making HTTP requests.
 ///
 /// The easiest way to use this library is via the top-level functions. They
 /// allow you to make individual HTTP requests with minimal hassle:
 ///
 ///     import 'package:http/http.dart' as http;
@@ skipping 19 matching lines @@
 ///       .transform((response) => print(response.body))
 ///       .onComplete((_) => client.close());
 ///
 /// You can also exert more fine-grained control over your requests and
 /// responses by creating [Request] or [StreamedRequest] objects yourself and
 /// passing them to [Client.send].
 ///
 /// This package is designed to be composable. This makes it easy for external
 /// libraries to work with one another to add behavior to it. Libraries wishing
 /// to add behavior should create a subclass of [BaseClient] that wraps another
-/// [BaseClient] and adds the desired behavior:
+/// [Client] and adds the desired behavior:
 ///
 ///     class UserAgentClient extends http.BaseClient {
 ///       final String userAgent;
-///       final HttpClient _inner;
+///       final http.Client _inner;
 ///
 ///       UserAgentClient(this.userAgent, this._inner);
 ///
 ///       Future<StreamedResponse> send(BaseRequest request) {
 ///         request.headers[HttpHeaders.USER_AGENT] = userAgent;
 ///         return _inner.send(request);
 ///       }
 ///     }
-///
-/// In turn, libraries using [Client] should take a [BaseClient] so that the
-/// decorated clients can be used transparently.
 
 library http;
 
 import 'dart:scalarlist';
 import 'dart:uri';
 
 import 'src/client.dart';
 import 'src/response.dart';
 
 export 'src/base_client.dart';
@@ skipping 101 matching lines @@
 /// instead.
 Future<Uint8List> readBytes(url, {Map<String, String> headers}) =>
   _withClient((client) => client.readBytes(url, headers: headers));
 
 Future _withClient(Future fn(Client)) {
   var client = new Client();
   var future = fn(client);
   future.onComplete((_) => client.close());
   return future;
 }