Allow assertions to be enabled in Blink Release builds.

Source/wtf/RefCountedLeakCounter.h

 /*
  *  Copyright (C) 2008 Apple Inc. All rights reserved.
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  *  Library General Public License for more details.
  *
  *  You should have received a copy of the GNU Library General Public License
  *  along with this library; see the file COPYING.LIB.  If not, write to
  *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  *  Boston, MA 02110-1301, USA.
  *
  */
 
 #ifndef RefCountedLeakCounter_h
 #define RefCountedLeakCounter_h
 
+#include "wtf/Assertions.h"
 #include "wtf/WTFExport.h"
 
 namespace WTF {
 
     struct WTF_EXPORT RefCountedLeakCounter {
         static void suppressMessages(const char*);
         static void cancelMessageSuppression(const char*);
 
         explicit RefCountedLeakCounter(const char* description);
         ~RefCountedLeakCounter();
 
         void increment();
         void decrement();
 
-#ifndef NDEBUG
+#if ENABLE(ASSERT)
     private:
         volatile int m_count;
         const char* m_description;
 #endif
     };
 
 }  // namespace WTF
 
 #endif