Fix UTF8 encoder for Unicode runes > 0xFFFF.

tests/lib/convert/utf85_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.
 
+library utf8_test;
 import "package:expect/expect.dart";
 import 'dart:convert';
-import 'unicode_tests.dart';
-
-String decode(List<int> bytes) => new Utf8Decoder().convert(bytes);
 
 main() {
-  for (var test in UNICODE_TESTS) {
-    List<int> bytes = test[0];
-    String expected = test[1];
-    Expect.stringEquals(expected, decode(bytes));
-  }
+   for (int i = 0; i <= 0x10FFFF; i++) {
+     if (i == UNICODE_BOM_CHARACTER_RUNE) continue;
+     Expect.equals(i,
+        UTF8.decode(UTF8.encode(new String.fromCharCode(i))).runes.first);
+   }
 }