Type check when upcasting PassOwnPtr/PassOwnArrayPtr to avoid possible function call ambiguousness

Source/wtf/PassOwnPtr.h

Index: Source/wtf/PassOwnPtr.h
diff --git a/Source/wtf/PassOwnPtr.h b/Source/wtf/PassOwnPtr.h
index c379f2fd3d6777b6be6f0202f08953e2e1faaf65..3e2913ef5655e502b8476d395909e5f7c5936696 100644
--- a/Source/wtf/PassOwnPtr.h
+++ b/Source/wtf/PassOwnPtr.h
@@ -52,7 +52,7 @@ namespace WTF {
         // a const PassOwnPtr. However, it makes it much easier to work with PassOwnPtr
         // temporaries, and we don't have a need to use real const PassOwnPtrs anyway.
         PassOwnPtr(const PassOwnPtr& o) : m_ptr(o.leakPtr()) { }
-        template<typename U> PassOwnPtr(const PassOwnPtr<U>& o) : m_ptr(o.leakPtr()) { }
+        template<typename U> PassOwnPtr(const PassOwnPtr<U>& o, EnsurePtrConvertibleArgDecl(typename RemovePointer<U>::Type, ValueType)) : m_ptr(o.leakPtr()) { }
 
         ~PassOwnPtr() { deleteOwnedPtr(m_ptr); }