Reland: WTF: Implement explicit 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 53 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; }
 
-    // This conversion operator allows implicit conversion to bool but not to
-    // other integer types.
-    typedef T* (RefPtr::*UnspecifiedBoolType);
-    operator UnspecifiedBoolType() const { return m_ptr ? &RefPtr::m_ptr : 0; }
+    // 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 40 matching lines @@
 template <typename T, typename U> inline bool operator==(const RefPtr<T>& a, U* b)
 {
     return a.get() == b;
 }
 
 template <typename T, typename U> inline bool operator==(T* a, const RefPtr<U>& b)
 {
     return a == b.get();
 }
 
+template <typename T> inline bool operator==(const RefPtr<T>& a, std::nullptr_t)
+{
+    return !a.get();
+}
+
+template <typename T> inline bool operator==(std::nullptr_t, const RefPtr<T>& b)
+{
+    return !b.get();
+}
+
 template <typename T, typename U> inline bool operator!=(const RefPtr<T>& a, const RefPtr<U>& b)
 {
     return a.get() != b.get();
 }
 
 template <typename T, typename U> inline bool operator!=(const RefPtr<T>& a, U* b)
 {
     return a.get() != b;
 }
 
 template <typename T, typename U> inline bool operator!=(T* a, const RefPtr<U>& b)
 {
     return a != b.get();
 }
 
+template <typename T> inline bool operator!=(const RefPtr<T>& a, std::nullptr_t)
+{
+    return a.get();
+}
+
+template <typename T> inline bool operator!=(std::nullptr_t, const RefPtr<T>& b)
+{
+    return b.get();
+}
+
 template <typename T, typename U> inline RefPtr<T> static_pointer_cast(const RefPtr<U>& p)
 {
     return RefPtr<T>(static_cast<T*>(p.get()));
 }
 
 template <typename T> inline T* getPtr(const RefPtr<T>& p)
 {
     return p.get();
 }
 
 template <typename T> class RefPtrValuePeeker {
     DISALLOW_NEW();
 public:
     ALWAYS_INLINE RefPtrValuePeeker(T* p): m_ptr(p) {}
     ALWAYS_INLINE RefPtrValuePeeker(std::nullptr_t): m_ptr(nullptr) {}
     template <typename U> RefPtrValuePeeker(const RefPtr<U>& p): m_ptr(p.get()) {}
     template <typename U> RefPtrValuePeeker(const PassRefPtr<U>& p): m_ptr(p.get()) {}
 
     ALWAYS_INLINE operator T*() const { return m_ptr; }
 private:
     T* m_ptr;
 };
 
 } // namespace WTF
 
 using WTF::RefPtr;
 using WTF::static_pointer_cast;
 
 #endif // WTF_RefPtr_h