Fix shelf_web_socket's Connection handling.

pkg/shelf_web_socket/test/web_socket_test.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_web_socket.web_socket_test;
 
 import 'dart:io';
 
 import 'package:http/http.dart' as http;
 import 'package:shelf/shelf_io.dart' as shelf_io;
@@ skipping 87 matching lines @@
       expect(http.get(url, headers: headers), hasStatus(101));
     });
 
     test("ignores the case of the server origin", () {
       var headers = _handshakeHeaders;
       headers['Origin'] = 'google.com';
       expect(http.get(url, headers: headers), hasStatus(101));
     });
   });
 
+  // Regression test for issue 21894.
+  test("allows a Connection header with multiple values", () {
+    return shelf_io.serve(webSocketHandler((webSocket) {
+      webSocket.close();
+    }), "localhost", 0).then((server) {
+      var url = 'http://localhost:${server.port}/';
+
+      var headers = _handshakeHeaders;
+      headers['Connection'] = 'Other-Token, Upgrade';
+      expect(http.get(url, headers: headers).whenComplete(server.close),
+          hasStatus(101));
+    });
+  });
+
   group("HTTP errors", () {
     var server;
     var url;
     setUp(() {
       return shelf_io.serve(webSocketHandler((_) {
         fail("should not create a WebSocket");
       }), "localhost", 0).then((server_) {
         server = server_;
         url = 'http://localhost:${server.port}/';
       });
@@ skipping 40 matching lines @@
     expect(() => webSocketHandler((_) => null, protocols: ['foo']),
         throwsArgumentError);
   });
 }
 
 Matcher hasStatus(int status) => completion(predicate((response) {
   expect(response, new isInstanceOf<http.Response>());
   expect(response.statusCode, equals(status));
   return true;
 }));