Remove DocumentLifecycle::Scope's setFinalState, nothing uses it.

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 c406fa853e34160104c339adc6258d28cf50fd58..44d4650b545a44a80f45f5fa01e5bc32f787a9d7 100644
--- a/Source/core/dom/DocumentLifecycle.h
+++ b/Source/core/dom/DocumentLifecycle.h
@@ -84,8 +84,6 @@ public:
         Scope(DocumentLifecycle&, State finalState);
         ~Scope();
 
-        void setFinalState(State finalState) { m_finalState = finalState; }
-
     private:
         DocumentLifecycle& m_lifecycle;
         State m_finalState;