[New Multicolumn] Make positionForPoint() work.

Source/core/layout/LayoutMultiColumnSet.h

 /*
  * Copyright (C) 2012 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 48 matching lines @@
 // fragmentainer (page / column) that the inner multicol container lives in. Each fragmentainer
 // group has its own column height, but the column height is uniform within a group.
 class LayoutMultiColumnSet : public LayoutRegion {
 public:
     static LayoutMultiColumnSet* createAnonymous(LayoutFlowThread&, const LayoutStyle& parentStyle);
 
     const MultiColumnFragmentainerGroup& firstFragmentainerGroup() const { return m_fragmentainerGroups.first(); }
     const MultiColumnFragmentainerGroup& lastFragmentainerGroup() const { return m_fragmentainerGroups.last(); }
     MultiColumnFragmentainerGroup& fragmentainerGroupAtFlowThreadOffset(LayoutUnit);
     const MultiColumnFragmentainerGroup& fragmentainerGroupAtFlowThreadOffset(LayoutUnit) const;
+    const MultiColumnFragmentainerGroup& fragmentainerGroupAtVisualPoint(const LayoutPoint&) const;
 
     virtual bool isOfType(LayoutObjectType type) const override { return type == LayoutObjectLayoutMultiColumnSet || LayoutRegion::isOfType(type); }
 
     virtual LayoutUnit pageLogicalWidth() const final { return flowThread()->logicalWidth(); }
     virtual LayoutUnit pageLogicalHeight() const final;
 
     LayoutBlockFlow* multiColumnBlockFlow() const { return toLayoutBlockFlow(parent()); }
     LayoutMultiColumnFlowThread* multiColumnFlowThread() const
     {
         ASSERT_WITH_SECURITY_IMPLICATION(!flowThread() || flowThread()->isLayoutMultiColumnFlowThread());
@@ skipping 72 matching lines @@
 protected:
     LayoutMultiColumnSet(LayoutFlowThread*);
 
 private:
     virtual void insertedIntoTree() override final;
     virtual void willBeRemovedFromTree() override final;
 
     virtual bool isSelfCollapsingBlock() const override { return false; }
 
     virtual void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues&) const override;
+    virtual PositionWithAffinity positionForPoint(const LayoutPoint&) override;
 
     virtual void paintObject(const PaintInfo&, const LayoutPoint& paintOffset) override;
 
     virtual void addOverflowFromChildren() override;
 
     virtual LayoutRect flowThreadPortionRect() const override;
 
     MultiColumnFragmentainerGroupList m_fragmentainerGroups;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutMultiColumnSet, isLayoutMultiColumnSet());
 
 } // namespace blink
 
 #endif // LayoutMultiColumnSet_h