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

tests/standalone/io/raw_secure_server_socket_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 "dart:async";
@@ skipping 455 matching lines @@
 
   if (listenSecure) {
     RawSecureServerSocket.bind(
         HOST_NAME, 0, CERTIFICATE).then(serverReady);
   } else {
     RawServerSocket.bind(HOST_NAME, 0).then(serverReady);
   }
 }
 
 main() {
-  var certificateDatabase = Platform.script.resolve('pkcert').toFilePath();
+  var certificateDatabase = join(dirname(Platform.script), 'pkcert');
   SecureSocket.initialize(database: certificateDatabase,
                           password: 'dartdart',
                           useBuiltinRoots: false);
   testSimpleBind();
   testInvalidBind();
   testSimpleConnect(CERTIFICATE);
   testSimpleConnect("CN=localhost");
   testSimpleConnectFail("not_a_nickname", false);
   testSimpleConnectFail("CN=notARealDistinguishedName", false);
   testSimpleConnectFail("not_a_nickname", true);
@@ skipping 33 matching lines @@
                       connectSecure: true,
                       handshakeBeforeSecure: false,
                       postponeSecure: false,
                       dropReads: true);
   testSimpleReadWrite(listenSecure: false,
                       connectSecure: false,
                       handshakeBeforeSecure: true,
                       postponeSecure: true,
                       dropReads: true);
 }