pkg/shelf: fix for UnmodifiableMapView collision in bleeding edge dart:collection

pkg/shelf/lib/src/request.dart

 // Copyright (c) 2014, 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 shelf.request;
 
 import 'dart:async';
 import 'dart:collection';
 
-import 'package:collection/wrappers.dart';
+// TODO(kevmoo): use UnmodifiableMapView from SDK once 1.4 ships
+import 'package:collection/wrappers.dart' as pc;
 import 'package:path/path.dart' as p;
 
 import 'message.dart';
 import 'util.dart';
 
 /// Represents an HTTP request to be processed by a Shelf application.
 class Request extends Message {
   /// The remainder of the [requestedUri] path designating the virtual
   /// "location" of the request's target within the handler.
   ///
@@ skipping 41 matching lines @@
     if (!headers.containsKey('if-modified-since')) return null;
     _ifModifiedSinceCache = parseHttpDate(headers['if-modified-since']);
     return _ifModifiedSinceCache;
   }
   DateTime _ifModifiedSinceCache;
 
   Request(this.pathInfo, String queryString, this.method,
       this.scriptName, this.protocolVersion, this.requestedUri,
       Map<String, String> headers, {Stream<List<int>> body})
       : this.queryString = queryString == null ? '' : queryString,
-        super(new UnmodifiableMapView(new HashMap.from(headers)),
+        super(new pc.UnmodifiableMapView(new HashMap.from(headers)),
             body == null ? new Stream.fromIterable([]) : body) {
     if (method.isEmpty) throw new ArgumentError('method cannot be empty.');
 
     if (scriptName.isNotEmpty && !scriptName.startsWith('/')) {
       throw new ArgumentError('scriptName must be empty or start with "/".');
     }
 
     if (scriptName == '/') {
       throw new ArgumentError(
           'scriptName can never be "/". It should be empty instead.');
@@ skipping 15 matching lines @@
   /// Convenience property to access [pathInfo] data as a [List].
   List<String> get pathSegments {
     var segs = p.url.split(pathInfo);
     if (segs.length > 0) {
       assert(segs.first == p.url.separator);
       segs.removeAt(0);
     }
     return segs;
   }
 }