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

Source/wtf/OwnPtr.h

Index: Source/wtf/OwnPtr.h
diff --git a/Source/wtf/OwnPtr.h b/Source/wtf/OwnPtr.h
index 0bda99bf18f1e8191734330a31d818767f1d16dc..f14ccf107ea2f8f8f5e903809b0dcffc3246cc41 100644
--- a/Source/wtf/OwnPtr.h
+++ b/Source/wtf/OwnPtr.h
@@ -50,7 +50,7 @@ namespace WTF {
         OwnPtr(std::nullptr_t) : m_ptr(0) { }
 
         // See comment in PassOwnPtr.h for why this takes a const reference.
-        template<typename U> OwnPtr(const PassOwnPtr<U>& o);
+        template<typename U> OwnPtr(const PassOwnPtr<U>&, EnsureOwnPtrConvertibleArgDecl);
 
 #if !COMPILER_SUPPORTS(CXX_RVALUE_REFERENCES)
         // This copy constructor is used implicitly by gcc when it generates
@@ -107,7 +107,7 @@ namespace WTF {
         PtrType m_ptr;
     };
 
-    template<typename T> template<typename U> inline OwnPtr<T>::OwnPtr(const PassOwnPtr<U>& o)
+    template<typename T> template<typename U> inline OwnPtr<T>::OwnPtr(const PassOwnPtr<U>& o, EnsureOwnPtrConvertibleArgDefn)
         : m_ptr(o.leakPtr())
     {
     }