Fix for running with --throw_on_javascript_int_overflow: recognize pattern (a << b) & mask and test…

runtime/lib/object_patch.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.
 
 patch class Object {
 
   // Helpers used to implement hashCode. If a hashCode is used, we remember it
   // in a weak table in the VM. A new hashCode value is calculated using a
   // number generator.
   static final _hashCodeRnd = new Random();
@@ skipping 52 matching lines @@
 
   static _symbolMapToStringMap(Map<Symbol, dynamic> map) {
     var result = new Map<String, dynamic>();
     map.forEach((Symbol key, value) {
       result[_collection_dev.Symbol.getName(key)] = value;
     });
     return result;
   }
 
   int get _cid native "Object_cid";
+
+  _leftShiftWithMask32(count, mask)  {
+    return (this << count) & mask;
+  }
 }