Implement FullScreen using top layer.

Source/core/dom/Fullscreen.h

Index: Source/core/dom/Fullscreen.h
diff --git a/Source/core/dom/Fullscreen.h b/Source/core/dom/Fullscreen.h
index 8e8a8639599dcab5fb172f6a40c6c99a23332d2b..5ae575125598ebdccb8dd23caf3d13fa9ec896ad 100644
--- a/Source/core/dom/Fullscreen.h
+++ b/Source/core/dom/Fullscreen.h
@@ -41,7 +41,6 @@
 
 namespace blink {
 
-class LayoutFullScreen;
 class ComputedStyle;
 
 class CORE_EXPORT Fullscreen final
@@ -78,10 +77,6 @@ public:
     void didEnterFullScreenForElement(Element*);
     void didExitFullScreenForElement(Element*);
 
-    void setFullScreenLayoutObject(LayoutFullScreen*);
-    LayoutFullScreen* fullScreenLayoutObject() const { return m_fullScreenLayoutObject; }
-    void fullScreenLayoutObjectDestroyed();
-
     void elementRemoved(Element&);
 
     // Mozilla API
@@ -94,6 +89,8 @@ public:
 
     DECLARE_VIRTUAL_TRACE();
 
+    const WillBeHeapVector<std::pair<RefPtrWillBeMember<Element>, RequestType>>& fullScreenElementStack() { return m_fullScreenElementStack; }
+
 private:
     static Fullscreen* fromIfExistsSlow(Document&);
 
@@ -111,7 +108,6 @@ private:
 
     RefPtrWillBeMember<Element> m_fullScreenElement;
     WillBeHeapVector<std::pair<RefPtrWillBeMember<Element>, RequestType>> m_fullScreenElementStack;
-    LayoutFullScreen* m_fullScreenLayoutObject;
     Timer<Fullscreen> m_eventQueueTimer;
     WillBeHeapDeque<RefPtrWillBeMember<Event>> m_eventQueue;
     LayoutRect m_savedPlaceholderFrameRect;