Recognize and special case String.fromCharCodes for Uint8List in JavaScript.

tests/corelib/string_fromcharcodes_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.
 
 import "package:expect/expect.dart";
 import "dart:typed_data";
 
 main() {
   iter(count, [values]) => values is List
                                ? new Iterable.generate(count, (x) => values[x])
@@ skipping 175 matching lines @@
     }
   }
 
   testSubstring("");
   testSubstring("ABCDEFGH");
   // length > 128
   testSubstring("ABCDEFGH" * 33);
   testSubstring("\x00" * 357);
   // length > 128 and non-ASCII.
   testSubstring("\uFFFD\uFFFE\u{10000}\u{10ffff}c\x00" * 37);
+
+  // Large List.
+  var megaList = ("abcde" * 200000).codeUnits.toList();
+  test("abcde" * 199998, megaList, 5, 999995);
+  // Large Uint8List.
+  test("abcde" * 199998, new Uint8List.fromList(megaList), 5, 999995);
 }