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

pkg/scheduled_test/test/scheduled_process_test.dart

Index: pkg/scheduled_test/test/scheduled_process_test.dart
diff --git a/pkg/scheduled_test/test/scheduled_process_test.dart b/pkg/scheduled_test/test/scheduled_process_test.dart
index 74d8cd629a50203d51c6e20d06a1d2ef848528e1..e09c536824ac868bd66ece8420e6ed90f2c1b482 100644
--- a/pkg/scheduled_test/test/scheduled_process_test.dart
+++ b/pkg/scheduled_test/test/scheduled_process_test.dart
@@ -365,6 +365,7 @@ ScheduledProcess startDartProcess(String script) {
                          'create temp dir');
   var dartPath = schedule(() {
     return tempDir.then((dir) {
+      var utilsPath = path.absolute(path.join(Platform.script, 'utils.dart'));
       return new File(path.join(dir, 'test.dart')).writeAsString('''
           import 'dart:async';
           import 'dart:convert';