Remove the old multicol implementation.

Source/core/layout/LayoutView.h

Index: Source/core/layout/LayoutView.h
diff --git a/Source/core/layout/LayoutView.h b/Source/core/layout/LayoutView.h
index dbc2e1442692718244364db6345978a940f5b5b0..15a6336644a7d1ec3825b045b9b9edd73be691bb 100644
--- a/Source/core/layout/LayoutView.h
+++ b/Source/core/layout/LayoutView.h
@@ -68,8 +68,6 @@ public:
     virtual void updateLogicalWidth() override;
     virtual void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues&) const override;
 
-    virtual LayoutUnit availableLogicalHeight(AvailableLogicalHeightType) const override;
-
     // Based on FrameView::layoutSize, but:
     // - checks for null FrameView
     // - returns 0x0 if using printing layout
@@ -146,7 +144,6 @@ public:
     bool usesCompositing() const;
 
     IntRect unscaledDocumentRect() const;
-    LayoutRect backgroundRect(LayoutBox* backgroundLayoutObject) const;
 
     IntRect documentRect() const;