Update dart:io to convert strings between UTF8 and current code page

tests/standalone/float_array_test.dart

 // 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.
 //
 // Dart test program for testing native float arrays.
 
 // Library tag to be able to run in html test framework.
 #library("FloatArrayTest.dart");
 
 #import('dart:scalarlist');
@@ skipping 195 matching lines @@
   testBadValues32();
   testBadValues64();
   // Check optimized (inlined) version of []=
   Expect.throws(() {
     storeIt32(a32, 1, 2);
   });
   Expect.throws(() {
     storeIt64(a64, 1, 2);
   });
 }