Migrate test block 30 + corelib portion of block 31 to Dart 2.0.

tests/corelib_2/uri_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 uriTest;
 
 import "package:expect/expect.dart";
 import 'dart:convert';
 
 testUri(String uriText, bool isAbsolute) {
@@ skipping 622 matching lines @@
 String dump(Uri uri) {
   return "URI: $uri\n"
       "  Scheme:    ${uri.scheme} #${uri.scheme.length}\n"
       "  User-info: ${uri.userInfo} #${uri.userInfo.length}\n"
       "  Host:      ${uri.host} #${uri.host.length}\n"
       "  Port:      ${uri.port}\n"
       "  Path:      ${uri.path} #${uri.path.length}\n"
       "  Query:     ${uri.query} #${uri.query.length}\n"
       "  Fragment:  ${uri.fragment} #${uri.fragment.length}\n";
 }