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

tests/standalone/io/skipping_dart2js_compilations_test.dart

Index: tests/standalone/io/skipping_dart2js_compilations_test.dart
diff --git a/tests/standalone/io/skipping_dart2js_compilations_test.dart b/tests/standalone/io/skipping_dart2js_compilations_test.dart
index b41dc75a8df4fe6209716f1e4d1d4b3739eecd5e..06efd120662ca733595a07c6f3d95377d70e0dd4 100644
--- a/tests/standalone/io/skipping_dart2js_compilations_test.dart
+++ b/tests/standalone/io/skipping_dart2js_compilations_test.dart
@@ -148,8 +148,8 @@ class CommandCompletedHandler {
 
 runner.Command makeCompilationCommand(String testName, FileUtils fileUtils) {
   var config = new options.TestOptionsParser().parse(['--timeout', '2'])[0];
-  var createFileScript = join(dirname(Platform.script),
-      'skipping_dart2js_compilations_helper.dart');
+  var createFileScript = Platform.script
+      .resolve('skipping_dart2js_compilations_helper.dart').toFilePath();
   var executable = Platform.executable;
   var arguments = [createFileScript, fileUtils.scriptOutputPath.toNativePath()];
   var bootstrapDeps = [