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

tests/standalone/io/stdin_sync_test.dart

Index: tests/standalone/io/stdin_sync_test.dart
diff --git a/tests/standalone/io/stdin_sync_test.dart b/tests/standalone/io/stdin_sync_test.dart
index 5d14509dd7e41d03fc6fe759144b09844c7946aa..63e4f1dde1c8410b249e6505be0d937b7fad7f59 100644
--- a/tests/standalone/io/stdin_sync_test.dart
+++ b/tests/standalone/io/stdin_sync_test.dart
@@ -9,7 +9,7 @@ import "package:path/path.dart";
 
 void testReadByte() {
   void test(String line, List<String> expected) {
-    var script = join(dirname(Platform.script), "stdin_sync_script.dart");
+    var script = Platform.script.resolve("stdin_sync_script.dart").toFilePath();
     Process.start(Platform.executable,
                   ["--checked", script]..addAll(
                       expected.map(JSON.encode))).then((process) {