Purge UnspecifiedBoolType from Blink.

third_party/WebKit/Source/wtf/WeakPtr.h

 /*
  * Copyright (C) 2013 Google, 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 89 matching lines @@
         DCHECK(get());
         return *get();
     }
 
     T* operator->() const
     {
         DCHECK(get());
         return get();
     }
 
-    typedef RefPtr<WeakReference<T>> (WeakPtr::*UnspecifiedBoolType);
-    operator UnspecifiedBoolType() const { return get() ? &WeakPtr::m_ref : 0; }
+    explicit operator bool() const { return get(); }
 
 private:
     RefPtr<WeakReference<T>> m_ref;
 };
 
 template<typename T, typename U> inline bool operator==(const WeakPtr<T>& a, const WeakPtr<U>& b)
 {
     return a.get() == b.get();
 }
 
@@ skipping 37 matching lines @@
     RefPtr<WeakReference<T>> m_ref;
 };
 
 } // namespace WTF
 
 using WTF::WeakPtr;
 using WTF::WeakPtrFactory;
 using WTF::WeakReference;
 
 #endif