Rename FullscreenElementStack to just Fullscreen

Source/core/page/EventHandler.h

Index: Source/core/page/EventHandler.h
diff --git a/Source/core/page/EventHandler.h b/Source/core/page/EventHandler.h
index a7683bd0605e27632b237dc65282eaded3c20d74..c3c0118f588b26f4d70c17e2467f614b3d7d4cb9 100644
--- a/Source/core/page/EventHandler.h
+++ b/Source/core/page/EventHandler.h
@@ -57,7 +57,7 @@ template <typename EventType>
 class EventWithHitTestResults;
 class FloatPoint;
 class FloatQuad;
-class FullscreenElementStack;
+class Fullscreen;
 class HTMLFrameSetElement;
 class HitTestRequest;
 class HitTestResult;
@@ -310,7 +310,7 @@ private:
 
     bool capturesDragging() const { return m_capturesDragging; }
 
-    bool isKeyEventAllowedInFullScreen(FullscreenElementStack*, const PlatformKeyboardEvent&) const;
+    bool isKeyEventAllowedInFullScreen(Fullscreen*, const PlatformKeyboardEvent&) const;
 
     bool handleGestureShowPress();