Remove more dead code from core/ folder

Source/core/page/FocusController.h

Index: Source/core/page/FocusController.h
diff --git a/Source/core/page/FocusController.h b/Source/core/page/FocusController.h
index 0983fcd5ce7589873dd3aef13ca5b4b72750fd37..97ae40264f991a1ff8c2edf735be75a2685725be 100644
--- a/Source/core/page/FocusController.h
+++ b/Source/core/page/FocusController.h
@@ -81,9 +81,6 @@ public:
     void setFocused(bool);
     bool isFocused() const { return m_isFocused; }
 
-    void setContainingWindowIsVisible(bool);
-    bool containingWindowIsVisible() const { return m_containingWindowIsVisible; }
-
 private:
     explicit FocusController(Page*);
 
@@ -119,8 +116,6 @@ private:
     bool m_isActive;
     bool m_isFocused;
     bool m_isChangingFocusedFrame;
-    bool m_containingWindowIsVisible;
-
 };
 
 } // namespace WebCore