Merge the dart:uri library into dart:core and update the Uri class

pkg/http/lib/src/base_request.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 base_request;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
-import 'dart:uri';
 
 import 'byte_stream.dart';
 import 'client.dart';
 import 'streamed_response.dart';
 import 'utils.dart';
 
 /// The base class for HTTP requests.
 ///
 /// Subclasses of [BaseRequest] can be constructed manually and passed to
 /// [BaseClient.send], which allows the user to provide fine-grained control
@@ skipping 105 matching lines @@
   }
 
   /// Throws an error if this request has been finalized.
   void _checkFinalized() {
     if (!finalized) return;
     throw new StateError("Can't modify a finalized Request.");
   }
 
   String toString() => "$method $url";
 }