Revert "Change dart:io Platform.script to return a Uri."

tests/standalone/io/web_socket_error_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
 
 library dart.io;
@@ skipping 72 matching lines @@
     });
   }
 
   void runTests() {
     testForceCloseServerEnd(10);
   }
 }
 
 
 void initializeSSL() {
-  var testPkcertDatabase = Platform.script.resolve('pkcert').toFilePath();
+  var testPkcertDatabase = join(dirname(Platform.script), 'pkcert');
   SecureSocket.initialize(database: testPkcertDatabase,
                           password: "dartdart");
 }
 
 
 main() {
   asyncStart();
   new SecurityConfiguration(secure: false).runTests();
   initializeSSL();
   new SecurityConfiguration(secure: true).runTests();
   asyncEnd();
 }