Reland: WTF: Implement explicit RefPtr::operator bool.

third_party/WebKit/Source/wtf/RefPtr.h

Index: third_party/WebKit/Source/wtf/RefPtr.h
diff --git a/third_party/WebKit/Source/wtf/RefPtr.h b/third_party/WebKit/Source/wtf/RefPtr.h
index 4ed3ea5de07c16ca00103e0044387d07421dbaef..eab641a66509aeca93b469c0f35c46e30c7ac44b 100644
--- a/third_party/WebKit/Source/wtf/RefPtr.h
+++ b/third_party/WebKit/Source/wtf/RefPtr.h
@@ -71,10 +71,9 @@ public:
 
     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; }
@@ -135,6 +134,16 @@ template <typename T, typename U> inline bool operator==(T* a, const RefPtr<U>&
     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();
@@ -150,6 +159,16 @@ template <typename T, typename U> inline bool operator!=(T* a, const RefPtr<U>&
     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()));