Bug 1627104 - Ensure Constructed StyleSheets' parent object is constructor document r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D69454

layout/style/StyleSheetInlines.h

@@ -24,6 +24,9 @@ void StyleSheet::SetURIs(nsIURI* aSheetURI, nsIURI* aOriginalSheetURI,
 }
 
 dom::ParentObject StyleSheet::GetParentObject() const {
+  if (IsConstructed()) {
+    return dom::ParentObject(mConstructorDocument.get());
+  }
   if (mOwningNode) {
     return dom::ParentObject(mOwningNode);
   }