Convert pkg/http to use "package:" imports.

pkg/http/test/streamed_request_test.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 streamed_request_test;
 
 import 'dart:io';
 
-import '../../unittest/lib/unittest.dart';
-import '../lib/http.dart' as http;
+import 'package:unittest/unittest.dart';
+import 'package:http/http.dart' as http;
 import 'utils.dart';
 
 void main() {
   test('#finalize freezes contentLength', () {
     var request = new http.StreamedRequest('POST', dummyUrl);
     request.finalize();
 
     expect(request.contentLength, equals(-1));
     expect(() => request.contentLength = 10, throwsStateError);
   });
 }