Clean up forward declarations in Source/platform

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 19 matching lines @@
 #include "platform/TraceLocation.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/Threading.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 // Time intervals are all in seconds.
 
-class TimerHeapElement;
-
 class PLATFORM_EXPORT TimerBase {
     WTF_MAKE_NONCOPYABLE(TimerBase); WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
 public:
     TimerBase();
     virtual ~TimerBase();
 
     void start(double nextFireInterval, double repeatInterval, const TraceLocation&);
 
     void startRepeating(double repeatInterval, const TraceLocation& caller)
     {
@@ skipping 137 matching lines @@
     TimerFiredClass* m_object;
     TimerFiredFunction m_function;
 
     double m_delay;
     bool m_shouldRestartWhenTimerFires;
 };
 
 }
 
 #endif