Replace RenderFullscreen with top layer - Take II

Source/core/rendering/RenderBox.h

Index: Source/core/rendering/RenderBox.h
diff --git a/Source/core/rendering/RenderBox.h b/Source/core/rendering/RenderBox.h
index 1b6ad9db06222269a7a77e1647ef28e2a1b8830e..b7a6715197c641ab1419fa75429748af3a216804 100644
--- a/Source/core/rendering/RenderBox.h
+++ b/Source/core/rendering/RenderBox.h
@@ -242,8 +242,8 @@ public:
 
     // IE extensions. Used to calculate offsetWidth/Height.  Overridden by inlines (RenderFlow)
     // to return the remaining width on a given line (and the height of a single line).
-    virtual LayoutUnit offsetWidth() const override { return m_frameRect.width(); }
-    virtual LayoutUnit offsetHeight() const override { return m_frameRect.height(); }
+    virtual LayoutUnit offsetWidth() const final { return m_frameRect.width(); }
+    virtual LayoutUnit offsetHeight() const final { return m_frameRect.height(); }
 
     virtual int pixelSnappedOffsetWidth() const override final;
     virtual int pixelSnappedOffsetHeight() const override final;
@@ -566,8 +566,8 @@ public:
     virtual LayoutUnit lineHeight(bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const override;
     virtual int baselinePosition(FontBaseline, bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const override;
 
-    virtual LayoutUnit offsetLeft() const override;
-    virtual LayoutUnit offsetTop() const override;
+    virtual LayoutUnit offsetLeft() const final;
+    virtual LayoutUnit offsetTop() const final;
 
     LayoutPoint flipForWritingModeForChild(const RenderBox* child, const LayoutPoint&) const;
     LayoutUnit flipForWritingMode(LayoutUnit position) const WARN_UNUSED_RETURN