Reland "Implement FullScreen using top layer."

third_party/WebKit/Source/core/layout/LayoutBox.h

Index: third_party/WebKit/Source/core/layout/LayoutBox.h
diff --git a/third_party/WebKit/Source/core/layout/LayoutBox.h b/third_party/WebKit/Source/core/layout/LayoutBox.h
index ca52d258eeabb66f7353e856939b932881e1c417..d402a3fcbc87c6d8987e98f3074e09ea33d4f89b 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.h
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.h
@@ -422,8 +422,8 @@ public:
 
     // IE extensions. Used to calculate offsetWidth/Height.  Overridden by inlines (LayoutFlow)
     // to return the remaining width on a given line (and the height of a single line).
-    LayoutUnit offsetWidth() const override { return m_frameRect.width(); }
-    LayoutUnit offsetHeight() const override { return m_frameRect.height(); }
+    LayoutUnit offsetWidth() const final { return m_frameRect.width(); }
+    LayoutUnit offsetHeight() const final { return m_frameRect.height(); }
 
     int pixelSnappedOffsetWidth(const Element*) const final;
     int pixelSnappedOffsetHeight(const Element*) const final;
@@ -836,8 +836,8 @@ public:
     LayoutUnit lineHeight(bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const override;
     int baselinePosition(FontBaseline, bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const override;
 
-    LayoutUnit offsetLeft(const Element*) const override;
-    LayoutUnit offsetTop(const Element*) const override;
+    LayoutUnit offsetLeft(const Element*) const final;
+    LayoutUnit offsetTop(const Element*) const final;
 
     LayoutPoint flipForWritingModeForChild(const LayoutBox* child, const LayoutPoint&) const;
     LayoutUnit flipForWritingMode(LayoutUnit position) const WARN_UNUSED_RETURN {