Refactor root element background painting

Source/core/layout/LayoutObject.h

Index: Source/core/layout/LayoutObject.h
diff --git a/Source/core/layout/LayoutObject.h b/Source/core/layout/LayoutObject.h
index 4b6eb3d5ad4ba6c7e3ff94bf5084c6d391e68aa7..e86dbbcf130210be4773309188a00d4dddfa60d0 100644
--- a/Source/core/layout/LayoutObject.h
+++ b/Source/core/layout/LayoutObject.h
@@ -1004,9 +1004,6 @@ public:
     // Compute a list of hit-test rectangles per layer rooted at this layoutObject.
     virtual void computeLayerHitTestRects(LayerHitTestRects&) const;
 
-    // Return the layoutObject whose background style is used to paint the root background. Should only be called on the layoutObject for which isDocumentElement() is true.
-    LayoutObject* layoutObjectForRootBackground();
-
     RespectImageOrientationEnum shouldRespectImageOrientation() const;
 
     bool isRelayoutBoundaryForInspector() const;