Paint solid color background into both scrolling contents layer and graphics layer.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google 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 29 matching lines @@
 
 enum PaintLayerType {
   NoPaintLayer,
   NormalPaintLayer,
   // A forced or overflow clip layer is required for bookkeeping purposes,
   // but does not force a layer to be self painting.
   OverflowClipPaintLayer,
   ForcedPaintLayer
 };
 
+enum : uint32_t {
+  BackgroundPaintInGraphicsLayer = 1 << 0,
+  BackgroundPaintInScrollingContents = 1 << 1
+};
+using BackgroundPaintLocation = uint32_t;
+
 // Modes for some of the line-related functions.
 enum LinePositionMode { PositionOnContainingLine, PositionOfInteriorLineBoxes };
 enum LineDirectionMode { HorizontalLine, VerticalLine };
 
 class InlineFlowBox;
 
 struct LayoutBoxModelObjectRareData {
   WTF_MAKE_NONCOPYABLE(LayoutBoxModelObjectRareData);
   USING_FAST_MALLOC(LayoutBoxModelObjectRareData);
 
@@ skipping 124 matching lines @@
   // border boxes.
   virtual IntRect borderBoundingBox() const = 0;
 
   virtual LayoutRect visualOverflowRect() const = 0;
 
   // Checks if this box, or any of it's descendants, or any of it's
   // continuations, will take up space in the layout of the page.
   bool hasNonEmptyLayoutSize() const;
   bool usesCompositedScrolling() const;
 
-  // Checks if all of the background's layers can be painted as locally
-  // attached.
-  bool hasLocalEquivalentBackground() const;
+  // Returns which layers backgrounds should be painted into for overflow
+  // scrolling boxes.
+  BackgroundPaintLocation backgroundPaintLocation() const;
 
   // These return the CSS computed padding values.
   LayoutUnit computedCSSPaddingTop() const {
     return computedCSSPadding(style()->paddingTop());
   }
   LayoutUnit computedCSSPaddingBottom() const {
     return computedCSSPadding(style()->paddingBottom());
   }
   LayoutUnit computedCSSPaddingLeft() const {
     return computedCSSPadding(style()->paddingLeft());
@@ skipping 313 matching lines @@
   std::unique_ptr<PaintLayer> m_layer;
 
   std::unique_ptr<LayoutBoxModelObjectRareData> m_rareData;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutBoxModelObject, isBoxModelObject());
 
 }  // namespace blink
 
 #endif  // LayoutBoxModelObject_h