Bug 1263782 - Kill off the deprecated nsINode::IsInDoc(). r=baku

dom/html/HTMLFormElement.cpp

@@ -1669,7 +1669,7 @@ HTMLFormElement::GetActionURL(nsIURI** aActionURL,
   // Get the document to form the URL.
   // We'll also need it later to get the DOM window when notifying form submit
   // observers (bug 33203)
-  if (!IsInDoc()) {
+  if (!IsInUncomposedDoc()) {
     return NS_OK; // No doc means don't submit, see Bug 28988
   }