Allow assertions to be enabled in Blink Release builds.

Source/platform/Timer.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 88 matching lines @@
     Vector<TimerBase*>& timerHeap() const { ASSERT(m_cachedThreadGlobalTimerHeap); return *m_cachedThreadGlobalTimerHeap; }
 
     double m_nextFireTime; // 0 if inactive
     double m_unalignedNextFireTime; // m_nextFireTime not considering alignment interval
     double m_repeatInterval; // 0 if not repeating
     int m_heapIndex; // -1 if not in heap
     unsigned m_heapInsertionOrder; // Used to keep order among equal-fire-time timers
     Vector<TimerBase*>* m_cachedThreadGlobalTimerHeap;
     TraceLocation m_location;
 
-#ifndef NDEBUG
+#if ENABLE(ASSERT)
     ThreadIdentifier m_thread;
 #endif
 
     friend class ThreadTimers;
     friend class TimerHeapLessThanFunction;
     friend class TimerHeapReference;
 };
 
 template <typename TimerFiredClass>
 class Timer FINAL : public TimerBase {
@@ skipping 69 matching lines @@
     TimerFiredClass* m_object;
     TimerFiredFunction m_function;
 
     double m_delay;
     bool m_shouldRestartWhenTimerFires;
 };
 
 }
 
 #endif