Fix File:openRead and file_input_stream_test.

tests/standalone/io/file_input_stream_test.dart

 // Copyright (c) 2013, 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.
 // Testing file input stream, VM-only, standalone test.
 
 import "dart:convert";
 import "dart:io";
 
 import "package:async_helper/async_helper.dart";
 import "package:expect/expect.dart";
@@ skipping 191 matching lines @@
 }
 
 
 void testInputStreamBadOffset() {
   void test(int start, int end) {
     asyncStart();
     var temp = Directory.systemTemp.createTempSync('file_input_stream_test');
     var file = new File('${temp.path}/input_stream_bad_offset.txt');
     var originalLength = writeLongFileSync(file);
     var streamedBytes = 0;
+    bool error = false;
     file.openRead(start, end).listen(
         (d) {
           streamedBytes += d.length;
         },
         onDone: () {
-          if (temp.existsSync()) {
-            temp.deleteSync(recursive: true);
-          }
+          Expect.isTrue(error);
+          temp.deleteSync(recursive: true);
+          asyncEnd();
         },
         onError: (e) {
-          if (temp.existsSync()) {
-            temp.deleteSync(recursive: true);
-          }
-          asyncEnd();
+          error = true;
         });
   }
   test(-1, null);
   test(100, 99);
   test(null, -1);
 }
 
 
 void testStringLineSplitterEnding(String name, int length) {
   String fileName = getFilename("tests/standalone/io/$name");
@@ skipping 25 matching lines @@
   testInputStreamDelete();
   testInputStreamAppend();
   testInputStreamOffset();
   testInputStreamBadOffset();
   // Check the length of these files as both are text files where one
   // is without a terminating line separator which can easily be added
   // back if accidentally opened in a text editor.
   testStringLineSplitterEnding("readline_test1.dat", 111);
   testStringLineSplitterEnding("readline_test2.dat", 114);
 }