Add browser-compatible version.

test/loader_file_test.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@TestOn("vm");
+
 import "dart:async";
 import "dart:convert";
 import "dart:io";
 
 import "package:resource/resource.dart";
 import "package:test/test.dart";
 
 const content = "Rødgrød med fløde";
 
-
 main() {
   var dir;
+  int dirCounter = 0;
   setUp(() {
-    dir = Directory.systemTemp.createTempSync('testdir');
+    dir = Directory.systemTemp.createTempSync('testdir${dirCounter++}');
   });
   testFile(Encoding encoding) {
     group("${encoding.name}", () {
       var file;
       var uri;
       setUp(() {
         var dirUri = dir.uri;
         uri = dirUri.resolve("file.txt");
         file = new File.fromUri(uri);
-        file.createSync();
-        var sink = file.openWrite(encoding: encoding);
-        sink.write(content);
-        sink.close();
+        file.writeAsBytesSync(encoding.encode(content));
       });
 
       test("read string", () async {
         var loader = ResourceLoader.defaultLoader;
         String string = await loader.readAsString(uri, encoding: encoding);
         expect(string, content);
       });
 
       test("read bytes", () async {
         var loader = ResourceLoader.defaultLoader;
@@ skipping 14 matching lines @@
       });
     });
   }
   testFile(LATIN1);
   testFile(UTF8);
 
   tearDown(() {
     dir.delete(recursive: true);
   });
 }