Revert of WTF: Simplify RefPtr::operator bool.

third_party/WebKit/Source/wtf/RefPtr.h

 /*
  *  Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2013 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
@@ skipping 52 matching lines @@
     {
         PassRefPtr<T> tmp = adoptRef(m_ptr);
         m_ptr = nullptr;
         return tmp;
     }
 
     T& operator*() const { return *m_ptr; }
     ALWAYS_INLINE T* operator->() const { return m_ptr; }
 
     bool operator!() const { return !m_ptr; }
-    explicit operator bool() const { return m_ptr; }
+
+    // TODO(jbroman): Simplifying this in the obvious way causes a massive
+    // regression in a perf test on ARM. http://crbug.com/607208
+    explicit operator bool() const { return m_ptr ? &RefPtr::m_ptr : 0; }
 
     RefPtr& operator=(RefPtr o) { swap(o); return *this; }
     RefPtr& operator=(std::nullptr_t) { clear(); return *this; }
     // This is required by HashMap<RefPtr>>.
     template <typename U> RefPtr& operator=(RefPtrValuePeeker<U>);
 
     void swap(RefPtr&);
 
     static T* hashTableDeletedValue() { return reinterpret_cast<T*>(-1); }
 
@@ skipping 104 matching lines @@
 private:
     T* m_ptr;
 };
 
 } // namespace WTF
 
 using WTF::RefPtr;
 using WTF::static_pointer_cast;
 
 #endif // WTF_RefPtr_h