Add ownerDocument to reachable list when needed. b=241518 r=bzbarsky sr=jst

content/base/src/nsGenericElement.cpp

@@ -1046,6 +1046,15 @@ nsGenericElement::GetSCCIndex()
 void
 nsGenericElement::AppendReachableList(nsCOMArray<nsIDOMGCParticipant>& aArray)
 {
+  NS_ASSERTION(GetCurrentDoc() == nsnull,
+               "shouldn't be an SCC index if we're in a doc");
+  NS_ASSERTION(GetOwnerDoc(), "no owner document");
+
+  // This node is the root of a subtree that's been removed from the
+  // document (since AppendReachableList is only called on SCC index
+  // nodes).  The document is reachable from it (through
+  // .ownerDocument), but it's not reachable from the document.
+  aArray.AppendObject(GetOwnerDoc());
 }
 
 NS_IMETHODIMP