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

Source/core/dom/DocumentLifecycle.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 66 matching lines @@
         Stopped,
         Disposed,
     };
 
     class Scope {
         WTF_MAKE_NONCOPYABLE(Scope);
     public:
         Scope(DocumentLifecycle&, State finalState);
         ~Scope();
 
-        void setFinalState(State finalState) { m_finalState = finalState; }
-
     private:
         DocumentLifecycle& m_lifecycle;
         State m_finalState;
     };
 
     class DeprecatedTransition {
         WTF_MAKE_NONCOPYABLE(DeprecatedTransition);
     public:
         DeprecatedTransition(State from, State to);
         ~DeprecatedTransition();
@@ skipping 99 matching lines @@
     return m_state != InPerformLayout
         && m_state != InCompositingUpdate
         && m_state != InPaintInvalidation
         && m_state != InPaintForSlimmingPaintV2
         && m_state != InCompositingForSlimmingPaintV2;
 }
 
 } // namespace blink
 
 #endif