Migrated test block 28 to Dart 2.0.

tests/corelib/string_source_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.
-
-// Test that different representations of the same string are all equal.
-
-import "dart:convert";
-
-import "package:expect/expect.dart";
-
-main() {
-  var base = "\u{10412}";
-  var strings = [
-    "\u{10412}",
-    "𐐒",
-    new String.fromCharCodes([0xd801, 0xdc12]),
-    base[0] + base[1],
-    "$base",
-    "${base[0]}${base[1]}",
-    "${base[0]}${base.substring(1)}",
-    new String.fromCharCodes([0x10412]),
-    ("a" + base).substring(1),
-    (new StringBuffer()..writeCharCode(0xd801)..writeCharCode(0xdc12))
-        .toString(),
-    (new StringBuffer()..writeCharCode(0x10412)).toString(),
-    JSON.decode('"\u{10412}"'),
-    (JSON.decode('{"\u{10412}":[]}') as Map).keys.first
-  ];
-  for (String string in strings) {
-    Expect.equals(base.length, string.length);
-    Expect.equals(base, string);
-    Expect.equals(base.hashCode, string.hashCode);
-    Expect.listEquals(base.codeUnits.toList(), string.codeUnits.toList());
-  }
-}