Change new List(n) to return fixed length list.

sdk/lib/isolate/mangler.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.
 
 part of dart.isolate;
 
 class _IsolateEncoder {
   final manglingToken;
   // TODO(floitsch): switch to identity set.
   final Map _encoded = new Map();
@@ skipping 26 matching lines @@
     _visiting[data] = data;
 
     var result;
 
     if (data is List) {
       bool hasBeenDuplicated = false;
       result = data;
       for (int i = 0; i < data.length; i++) {
         var mangled = encode(data[i]);
         if (mangled != data[i] && !hasBeenDuplicated) {
-          result = new List.fixedLength(data.length);
+          result = new List(data.length);
           for (int j = 0; j < i; j++) {
             result[j] = data[j];
           }
           hasBeenDuplicated = true;
         }
         if (hasBeenDuplicated) {
           result[i] = mangled;
         }
       }
       result = _escapeIfNecessary(result);
@@ skipping 203 matching lines @@
   }
   _extractMangled(wrappedMangled) {
     assert(_isMangled(wrappedMangled));
     return wrappedMangled[2];
   }
   _extractEscaped(data) {
     assert(_isEscaped(data));
     return data[2];
   }
 }