Output Element defaultValue should be based on textContent

Source/core/html/HTMLOutputElement.cpp

Index: Source/core/html/HTMLOutputElement.cpp
diff --git a/Source/core/html/HTMLOutputElement.cpp b/Source/core/html/HTMLOutputElement.cpp
index 6751780a06e96282178b4251820f8b51141941dd..76932d48cbc757effe3104de743f965ef36e8584 100644
--- a/Source/core/html/HTMLOutputElement.cpp
+++ b/Source/core/html/HTMLOutputElement.cpp
@@ -118,8 +118,10 @@ void HTMLOutputElement::setValue(const String& value)
     setTextContentInternal(value);
 }
 
-String HTMLOutputElement::defaultValue() const
+String HTMLOutputElement::defaultValue()
 {
+    if (m_isDefaultValueMode && m_defaultValue != value())
+        setDefaultValue(value());
     return m_defaultValue;
 }