Refactor root element background painting

Source/core/layout/LayoutView.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 125 matching lines @@
         }
     }
     bool pageLogicalHeightChanged() const { return m_pageLogicalHeightChanged; }
 
     // Notification that this view moved into or out of a native window.
     void setIsInWindow(bool);
 
     DeprecatedPaintLayerCompositor* compositor();
     bool usesCompositing() const;
 
+    // TODO(trchen): All pinch-zoom implementation should now use compositor raster scale based zooming,
+    // instead of LayoutView transform. Check whether we can now unify unscaledDocumentRect and documentRect.
     IntRect unscaledDocumentRect() const;
     LayoutRect backgroundRect(LayoutBox* backgroundLayoutObject) const;
 
     IntRect documentRect() const;
 
     // LayoutObject that paints the root background has background-images which all have background-attachment: fixed.
     bool rootBackgroundIsEntirelyFixed() const;
 
     IntervalArena* intervalArena();
 
@@ skipping 10 matching lines @@
 
     virtual bool backgroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect) const override;
 
     double layoutViewportWidth() const;
     double layoutViewportHeight() const;
 
     void pushLayoutState(LayoutState& layoutState) { m_layoutState = &layoutState; }
     void popLayoutState() { ASSERT(m_layoutState); m_layoutState = m_layoutState->next(); }
     virtual void invalidateTreeIfNeeded(PaintInvalidationState&) override final;
 
+    virtual LayoutRect visualOverflowRect() const override;
+
 private:
     virtual void mapLocalToContainer(const LayoutBoxModelObject* paintInvalidationContainer, TransformState&, MapCoordinatesFlags = ApplyContainerFlip, bool* wasFixed = nullptr, const PaintInvalidationState* = nullptr) const override;
     virtual const LayoutObject* pushMappingToContainer(const LayoutBoxModelObject* ancestorToStopAt, LayoutGeometryMap&) const override;
     virtual void mapAbsoluteToLocalPoint(MapCoordinatesFlags, TransformState&) const override;
     virtual void computeSelfHitTestRects(Vector<LayoutRect>&, const LayoutPoint& layerOffset) const override;
 
     void layoutContent();
 #if ENABLE(ASSERT)
     void checkLayoutState();
 #endif
 
     friend class ForceHorriblySlowRectMapping;
 
     bool shouldUsePrintingLayout() const;
 
-    LayoutObject* backgroundLayoutObject() const;
-
     int viewLogicalWidthForBoxSizing() const;
     int viewLogicalHeightForBoxSizing() const;
 
     FrameView* m_frameView;
 
     LayoutObject* m_selectionStart;
     LayoutObject* m_selectionEnd;
 
     int m_selectionStartPos;
     int m_selectionEndPos;
@@ skipping 36 matching lines @@
             m_paintInvalidationState->m_cachedOffsetsEnabled = true;
     }
 private:
     const PaintInvalidationState* m_paintInvalidationState;
     bool m_didDisable;
 };
 
 } // namespace blink
 
 #endif // LayoutView_h