Revert of WTF: Implement explicit RefPtr::operator bool.

third_party/WebKit/Source/wtf/PassRefPtr.h

Index: third_party/WebKit/Source/wtf/PassRefPtr.h
diff --git a/third_party/WebKit/Source/wtf/PassRefPtr.h b/third_party/WebKit/Source/wtf/PassRefPtr.h
index 7285b6cc00c971b63e86dfe2b0a078d30d633222..38dd9c9622bed23b92e1f44af1c45f80736a3c99 100644
--- a/third_party/WebKit/Source/wtf/PassRefPtr.h
+++ b/third_party/WebKit/Source/wtf/PassRefPtr.h
@@ -81,7 +81,11 @@
     T* operator->() const { return m_ptr; }
 
     bool operator!() const { return !m_ptr; }
-    explicit operator bool() const { return m_ptr; }
+
+    // This conversion operator allows implicit conversion to bool but not to
+    // other integer types.
+    typedef T* (PassRefPtr::*UnspecifiedBoolType);
+    operator UnspecifiedBoolType() const { return m_ptr ? &PassRefPtr::m_ptr : 0; }
 
     friend PassRefPtr adoptRef<T>(T*);
 
@@ -138,16 +142,6 @@
     return a == b.get();
 }
 
-template <typename T> inline bool operator==(const PassRefPtr<T>& a, std::nullptr_t)
-{
-    return !a.get();
-}
-
-template <typename T> inline bool operator==(std::nullptr_t, const PassRefPtr<T>& b)
-{
-    return !b.get();
-}
-
 template <typename T, typename U> inline bool operator!=(const PassRefPtr<T>& a, const PassRefPtr<U>& b)
 {
     return a.get() != b.get();
@@ -173,16 +167,6 @@
     return a != b.get();
 }
 
-template <typename T> inline bool operator!=(const PassRefPtr<T>& a, std::nullptr_t)
-{
-    return a.get();
-}
-
-template <typename T> inline bool operator!=(std::nullptr_t, const PassRefPtr<T>& b)
-{
-    return b.get();
-}
-
 template <typename T> PassRefPtr<T> adoptRef(T* p)
 {
     adopted(p);