Do not add shadow tree styles to stylist

components/script/dom/document.rs

@@ -4603,6 +4603,15 @@ impl StyleSheetListOwner for Dom<Document> {
                     .is_before(sheet_in_doc.owner.upcast())
             })
             .cloned();
+
+        self.window
+            .layout_chan()
+            .send(Msg::AddStylesheet(
+                sheet.clone(),
+                insertion_point.as_ref().map(|s| s.sheet.clone()),
+            ))
+            .unwrap();
+
         self.document_or_shadow_root.add_stylesheet(
             owner,
             stylesheets,

components/script/dom/documentorshadowroot.rs

@@ -253,14 +253,6 @@ impl DocumentOrShadowRoot {
             "Wat"
         );
 
-        self.window
-            .layout_chan()
-            .send(Msg::AddStylesheet(
-                sheet.clone(),
-                insertion_point.as_ref().map(|s| s.sheet.clone()),
-            ))
-            .unwrap();
-
         let sheet = StyleSheetInDocument {
             sheet,
             owner: Dom::from_ref(owner),