Allow String.fromCharCodes to work directly on a GrowableObjectArray.

runtime/lib/string_base.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.
 
 /**
  * [_StringBase] contains common methods used by concrete String
  * implementations, e.g., _OneByteString.
  */
 class _StringBase {
 
   factory _StringBase._uninstantiable() {
     throw new UnsupportedError(
         "_StringBase can't be instaniated");
   }
 
   int get hashCode native "String_getHashCode";
 
   /**
    *  Create the most efficient string representation for specified
    *  [codePoints].
    */
   static String createFromCharCodes(Iterable<int> charCodes) {
-    if (charCodes is! _ObjectArray) {
+    if (charCodes is! _ObjectArray && charCodes is! _GrowableObjectArray) {
       charCodes = new List<int>.from(charCodes, growable: false);
     }
     return _createFromCodePoints(charCodes);
   }
 
   static String _createFromCodePoints(List<int> codePoints)
       native "StringBase_createFromCodePoints";
 
   String operator [](int index) native "String_charAt";
 
@@ skipping 565 matching lines @@
     for (int g in groups) {
       result.add(group(g));
     }
     return result;
   }
 
   final int start;
   final String str;
   final String pattern;
 }