Drop support for old SDK and shelf versions.

lib/src/util/path_handler.dart

 // Copyright (c) 2015, 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 test.util.path_handler;
 
 import 'package:path/path.dart' as p;
 import 'package:shelf/shelf.dart' as shelf;
 
-import '../utils.dart';
-
 /// A handler that routes to sub-handlers based on exact path prefixes.
 class PathHandler {
   /// A trie of path components to handlers.
   final _paths = new _Node();
 
   /// The shelf handler.
   shelf.Handler get handler => _onRequest;
 
   PathHandler();
 
   /// Routes requests at or under [path] to [handler].
   ///
   /// If [path] is a parent or child directory of another path in this handler,
   /// the longest matching prefix wins.
   void add(String path, shelf.Handler handler) {
     var node = _paths;
     for (var component in p.url.split(path)) {
       node = node.children.putIfAbsent(component, () => new _Node());
     }
     node.handler = handler;
   }
 
   _onRequest(shelf.Request request) {
     var handler;
     var handlerIndex;
     var node = _paths;
-    var components = p.url.split(shelfUrl(request).path);
+    var components = p.url.split(request.url.path);
     for (var i = 0; i < components.length; i++ ) {
       node = node.children[components[i]];
       if (node == null) break;
       if (node.handler == null) continue;
       handler = node.handler;
       handlerIndex = i;
     }
 
     if (handler == null) return new shelf.Response.notFound("Not found.");
 
-    return handler(shelfChange(request,
+    return handler(request.change(
         path: p.url.joinAll(components.take(handlerIndex + 1))));
   }
 }
 
 /// A trie node.
 class _Node {
   shelf.Handler handler;
   final children = new Map<String, _Node>();
 }