Remove unused attachChildrenLazily method and make attach/detachChildren private

Source/core/dom/Element.cpp

Index: Source/core/dom/Element.cpp
diff --git a/Source/core/dom/Element.cpp b/Source/core/dom/Element.cpp
index 1528687e33dca215197c7352a68b8ab1e43089a9..316d18138c52a07d38e37ba929ce345936c26abb 100644
--- a/Source/core/dom/Element.cpp
+++ b/Source/core/dom/Element.cpp
@@ -1351,11 +1351,8 @@ void Element::detach(const AttachContext& context)
         data->resetComputedStyle();
         data->resetDynamicRestyleObservations();
     }
-
-    if (ElementShadow* shadow = this->shadow()) {
-        detachChildrenIfNeeded(context);
+    if (ElementShadow* shadow = this->shadow())
         shadow->detach(context);
-    }
     ContainerNode::detach(context);
 }