ASSERT on renderer lifecycle

Source/core/dom/DocumentLifecycle.h

Index: Source/core/dom/DocumentLifecycle.h
diff --git a/Source/core/dom/DocumentLifecycle.h b/Source/core/dom/DocumentLifecycle.h
index dcc6a6064614905b5be6f3eb3fe53c575bfee212..1869523f8879f3c5b0545b048d5c7ec2b548cea7 100644
--- a/Source/core/dom/DocumentLifecycle.h
+++ b/Source/core/dom/DocumentLifecycle.h
@@ -99,6 +99,7 @@ public:
     State state() const { return m_state; }
 
     bool stateAllowsTreeMutations() const;
+    bool stateAllowsRenderTreeMutations() const;
 
     void advanceTo(State);
     void ensureStateAtMost(State);
@@ -121,6 +122,11 @@ inline bool DocumentLifecycle::stateAllowsTreeMutations() const
         && m_state != InCompositingUpdate;
 }
 
+inline bool DocumentLifecycle::stateAllowsRenderTreeMutations() const
+{
+    return m_state == InStyleRecalc;
+}
+
 }
 
 #endif