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

tests/standalone/io/http_server_early_client_close2_test.dart

Index: tests/standalone/io/http_server_early_client_close2_test.dart
diff --git a/tests/standalone/io/http_server_early_client_close2_test.dart b/tests/standalone/io/http_server_early_client_close2_test.dart
index 055e2a06df31b881c64bbfed35dc42c76eaba90d..0f3f73bbb317d2bade667ae26b04fbcfbd2a0187 100644
--- a/tests/standalone/io/http_server_early_client_close2_test.dart
+++ b/tests/standalone/io/http_server_early_client_close2_test.dart
@@ -16,7 +16,7 @@ main() {
   HttpServer.bind("127.0.0.1", 0).then((server) {
     server.listen(
       (request) {
-        String name = Platform.script.toFilePath();
+        String name = Platform.script;
         new File(name).openRead().pipe(request.response)
             .catchError((e) { /* ignore */ });
       });