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

tests/standalone/io/resolve_symbolic_links_test.dart

Index: tests/standalone/io/resolve_symbolic_links_test.dart
diff --git a/tests/standalone/io/resolve_symbolic_links_test.dart b/tests/standalone/io/resolve_symbolic_links_test.dart
index 11b171c59359bb22cd5b03da470a13b7a11e1edd..252e65f5e362a6c3a10c82838d88d53f41c513c6 100644
--- a/tests/standalone/io/resolve_symbolic_links_test.dart
+++ b/tests/standalone/io/resolve_symbolic_links_test.dart
@@ -11,7 +11,7 @@ import 'dart:async';
 import 'dart:io';
 
 main() {
-  String testsDir = dirname(dirname(dirname(Platform.script)));
+  String testsDir = Platform.script.resolve('../..').toFilePath();
   // All of these tests test that resolveSymbolicLinks gives a path
   // that points to the same place as the original, and that it removes
   // all links, .., and . segments, and that it produces an absolute path.