Fix static type errors in a number of tests

tests/standalone/io/raw_server_socket_cancel_test.dart

 // Copyright (c) 2013, 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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
+import "package:expect/expect.dart";
 import "dart:async";
 import "dart:io";
 import "dart:isolate";
 
 void testCancelResubscribeServerSocket(int socketCount, int backlog) {
   var acceptCount = 0;
   var doneCount = 0;
   var closeCount = 0;
   var errorCount = 0;
   var earlyErrorCount = 0;
@@ skipping 75 matching lines @@
         checkDone();
       });
     }
   });
 }
 
 void main() {
   testCancelResubscribeServerSocket(10, 20);
   testCancelResubscribeServerSocket(20, 5);
 }