Change dart:io Platform.script to return a URI. Change all uses of Platform.script to work with th…

tests/standalone/io/socket_upgrade_to_secure_test.dart

Index: tests/standalone/io/socket_upgrade_to_secure_test.dart
diff --git a/tests/standalone/io/socket_upgrade_to_secure_test.dart b/tests/standalone/io/socket_upgrade_to_secure_test.dart
index efbc1434256bd156ea1f03d99c110fa975709428..ff0f7278d9830a9d035f8b34b9db1897ea2304ea 100644
--- a/tests/standalone/io/socket_upgrade_to_secure_test.dart
+++ b/tests/standalone/io/socket_upgrade_to_secure_test.dart
@@ -213,7 +213,7 @@ void test(bool hostnameInConnect,
 }
 
 main() {
-  var certificateDatabase = join(dirname(Platform.script), 'pkcert');
+  var certificateDatabase = Platform.script.resolve('pkcert').toFilePath();
   SecureSocket.initialize(database: certificateDatabase,
                           password: 'dartdart',
                           useBuiltinRoots: false);