Reland: 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 bd1ee380cfbf2ddb9eb92febda883694a687fd84..48538cd788a66d22bbbe934ef426f31801288f61 100644
--- a/third_party/WebKit/Source/wtf/PassRefPtr.h
+++ b/third_party/WebKit/Source/wtf/PassRefPtr.h
@@ -83,10 +83,9 @@ public:
 
     bool operator!() 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; }
+    // 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 ? &PassRefPtr::m_ptr : 0; }
 
     friend PassRefPtr adoptRef<T>(T*);
 
@@ -149,6 +148,16 @@ template <typename T, typename U> inline bool operator==(T* a, const PassRefPtr<
     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();
@@ -174,6 +183,16 @@ template <typename T, typename U> inline bool operator!=(T* a, const PassRefPtr<
     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);