VM: Fix fragile shaker test after changes to hash code storage.

runtime/vm/object.cc

 // 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.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/become.h"
@@ skipping 1021 matching lines @@
           if (counter_ == 0) counter_++;
           Object::SetCachedHash(obj, counter_);
         }
       }
 #endif
     }
   }
 
  private:
 #if defined(HASH_IN_OBJECT_HEADER)
-  int counter_;
+  int32_t counter_;
 #endif
 };
 
 
 #define SET_CLASS_NAME(class_name, name)                                       \
   cls = class_name##_class();                                                  \
   cls.set_name(Symbols::name());
 
 void Object::FinalizeVMIsolate(Isolate* isolate) {
   // Should only be run by the vm isolate.
@@ skipping 22493 matching lines @@
   return UserTag::null();
 }
 
 
 const char* UserTag::ToCString() const {
   const String& tag_label = String::Handle(label());
   return tag_label.ToCString();
 }
 
 }  // namespace dart