Make changing your layout manager work.

sky/engine/core/dom/Element.cpp

Index: sky/engine/core/dom/Element.cpp
diff --git a/sky/engine/core/dom/Element.cpp b/sky/engine/core/dom/Element.cpp
index 8537adb6d5e8cd8e4607ab5959d4f2b2b3877168..c3b6a981518ff0c3c2861d0d1ffbb9d540ae2890 100644
--- a/sky/engine/core/dom/Element.cpp
+++ b/sky/engine/core/dom/Element.cpp
@@ -971,6 +971,8 @@ void Element::setLayoutManager(PassOwnPtr<LayoutCallback> callback)
         // those are all tied to changes to the RenderStyle.
         markAncestorsWithChildNeedsStyleRecalc();
         detach();
+    } else if (callback.get() != m_layoutManager) {
+        setNeedsLayout();
     }
     m_layoutManager = callback;
 }