Make FileInputStream and FileOutputStream actually asynchronous.

tests/standalone/src/FileInvalidArgumentsTest.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2012, 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.
 
 #import("dart:io");
 
 class FileTest {
   static void testOpenInvalidArgs(name, [writable = false]) {
     var file = new File(name);
     try {
       file.openSync();
@@ skipping 85 matching lines @@
     } catch (var e) {
       Expect.isTrue(e is FileIOException);
       Expect.isTrue(e.toString().contains('Invalid argument'));
     }
 
     var errors = 0;
     file.errorHandler = (s) {
       errors++;
       Expect.isTrue(s.contains('Invalid argument'));
     };
-    file.noPendingWriteHandler = (bytes) {
-      Expect.fail('write list invalid argument');
+    var calls = 0;
+    file.noPendingWriteHandler = () {
+      if (++calls > 1) Expect.fail('write list invalid argument');
     };
     file.writeByte(value);
     file.closeHandler = () {
       Expect.equals(1, errors);
     };
     file.close();
   }
 
   static void testWriteListInvalidArgs(buffer, offset, bytes) {
     String filename = getFilename("tests/vm/data/fixed_length_file");
     var file = (new File(filename + "_out")).openSync(FileMode.WRITE);
     try {
       file.writeListSync(buffer, offset, bytes);
       Expect.fail('exception expected');
     } catch (var e) {
       Expect.isTrue(e is FileIOException);
       Expect.isTrue(e.toString().contains('Invalid arguments'));
     }
 
     var errors = 0;
     file.errorHandler = (s) {
       errors++;
       Expect.isTrue(s.contains('Invalid arguments'));
     };
-    file.noPendingWriteHandler = (bytes) {
-      Expect.fail('write list invalid argument');
+    var calls = 0;
+    file.noPendingWriteHandler = () {
+      if (++calls > 1) Expect.fail('write string invalid argument');
     };
     file.writeList(buffer, offset, bytes);
     file.closeHandler = () {
       Expect.equals(1, errors);
     };
     file.close();
   }
 
   static void testWriteStringInvalidArgs(string) {
     String filename = getFilename("tests/vm/data/fixed_length_file");
     var file = new File(filename + "_out");
     file.openSync(FileMode.WRITE);
     try {
       file.writeString(string);
       Expect.fail('exception expected');
     } catch (var e) {
       Expect.isTrue(e is FileIOException);
       Expect.isTrue(e.toString().contains('writeString failed'));
     }
 
     var errors = 0;
     file.errorHandler = (s) {
       errors++;
       Expect.isTrue(s.contains('writeString failed'));
     };
-    file.noPendingWriteHandler = (bytes) {
-      Expect.fail('write string invalid argument');
+    var calls = 0;
+    file.noPendingWriteHandler = () {
+      if (++calls > 1) Expect.fail('write list invalid argument');
     };
     file.writeString(string);
     file.closeHandler = () {
       Expect.equals(1, errors);
     };
     file.close();
   }
 
   static void testFullPathInvalidArgs(name) {
     var file = new File(name);
@@ skipping 25 matching lines @@
   FileTest.testCreateInvalidArgs(0);
   FileTest.testReadListInvalidArgs(12, 0, 1);
   FileTest.testReadListInvalidArgs(new List(10), '0', 1);
   FileTest.testReadListInvalidArgs(new List(10), 0, '1');
   FileTest.testWriteByteInvalidArgs('asdf');
   FileTest.testWriteListInvalidArgs(12, 0, 1);
   FileTest.testWriteListInvalidArgs(new List(10), '0', 1);
   FileTest.testWriteListInvalidArgs(new List(10), 0, '1');
   FileTest.testFullPathInvalidArgs(12);
 }