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

tests/standalone/io/file_read_stdio_script.dart

Index: tests/standalone/io/file_read_stdio_script.dart
diff --git a/tests/standalone/io/file_read_stdio_script.dart b/tests/standalone/io/file_read_stdio_script.dart
index 966d914b0b27f1bf3453408a2c3a6062e245c87f..948a0ec0c4ad08e4fc925d83ab775abbec52c66c 100644
--- a/tests/standalone/io/file_read_stdio_script.dart
+++ b/tests/standalone/io/file_read_stdio_script.dart
@@ -5,7 +5,7 @@
 import 'dart:io';
 
 void main() {
-  var expected = new File(Platform.script).readAsStringSync();
+  var expected = new File(Platform.script.toFilePath()).readAsStringSync();
   var stdin = new File('/dev/fd/0').readAsStringSync();
   if (expected != stdin) {
     throw "stdin not equal expected file";