Implement FullScreen using top layer.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 282 matching lines @@
     void updateLayerTransformAfterLayout();
 
     LayoutUnit contentWidth() const { return clientWidth() - paddingLeft() - paddingRight(); }
     LayoutUnit contentHeight() const { return clientHeight() - paddingTop() - paddingBottom(); }
     LayoutSize contentSize() const { return LayoutSize(contentWidth(), contentHeight()); }
     LayoutUnit contentLogicalWidth() const { return style()->isHorizontalWritingMode() ? contentWidth() : contentHeight(); }
     LayoutUnit contentLogicalHeight() const { return style()->isHorizontalWritingMode() ? contentHeight() : contentWidth(); }
 
     // 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 final;
     int pixelSnappedOffsetHeight() const final;
 
     // More IE extensions.  clientWidth and clientHeight represent the interior of an object
     // excluding border and scrollbar.  clientLeft/Top are just the borderLeftWidth and borderTopWidth.
     LayoutUnit clientLeft() const { return borderLeft() + (style()->shouldPlaceBlockDirectionScrollbarOnLogicalLeft() ? verticalScrollbarWidth() : 0); }
     LayoutUnit clientTop() const { return borderTop(); }
     LayoutUnit clientWidth() const;
     LayoutUnit clientHeight() const;
@@ skipping 314 matching lines @@
     bool isWritingModeRoot() const { return !parent() || parent()->style()->writingMode() != style()->writingMode(); }
 
     bool isDeprecatedFlexItem() const { return !isInline() && !isFloatingOrOutOfFlowPositioned() && parent() && parent()->isDeprecatedFlexibleBox(); }
     bool isFlexItemIncludingDeprecated() const { return !isInline() && !isFloatingOrOutOfFlowPositioned() && parent() && parent()->isFlexibleBoxIncludingDeprecated(); }
 
     bool isGridItem() const { return parent() && parent()->isLayoutGrid(); }
 
     LayoutUnit lineHeight(bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const override;
     int baselinePosition(FontBaseline, bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const override;
 
-    LayoutUnit offsetLeft() const override;
-    LayoutUnit offsetTop() const override;
+    LayoutUnit offsetLeft() const final;
+    LayoutUnit offsetTop() const final;
 
     LayoutPoint flipForWritingModeForChild(const LayoutBox* child, const LayoutPoint&) const;
     LayoutUnit flipForWritingMode(LayoutUnit position) const WARN_UNUSED_RETURN {
         // The offset is in the block direction (y for horizontal writing modes, x for vertical writing modes).
         if (!UNLIKELY(hasFlippedBlocksWritingMode()))
             return position;
         return logicalHeight() - position;
     }
     LayoutPoint flipForWritingMode(const LayoutPoint& position) const WARN_UNUSED_RETURN {
         if (!UNLIKELY(hasFlippedBlocksWritingMode()))
@@ skipping 305 matching lines @@
         if (UNLIKELY(inlineBoxWrapper() != nullptr))
             deleteLineBoxWrapper();
     }
 
     ensureRareData().m_inlineBoxWrapper = boxWrapper;
 }
 
 } // namespace blink
 
 #endif // LayoutBox_h