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

tests/standalone/io/raw_secure_server_socket_test.dart

Index: tests/standalone/io/raw_secure_server_socket_test.dart
diff --git a/tests/standalone/io/raw_secure_server_socket_test.dart b/tests/standalone/io/raw_secure_server_socket_test.dart
index 4226b80b8d983832ee555dd7a9ace6130b8b405d..44cb7fc19e581abb14cf29b8344ee9fbdbf77361 100644
--- a/tests/standalone/io/raw_secure_server_socket_test.dart
+++ b/tests/standalone/io/raw_secure_server_socket_test.dart
@@ -473,7 +473,7 @@ void testSimpleReadWrite({bool listenSecure,
 }
 
 main() {
-  var certificateDatabase = join(dirname(Platform.script), 'pkcert');
+  var certificateDatabase = Platform.script.resolve('pkcert').toFilePath();
   SecureSocket.initialize(database: certificateDatabase,
                           password: 'dartdart',
                           useBuiltinRoots: false);