[New Multicolumn] mapAbsoluteToLocalPoint() needs to convert to flow thread coordinates.

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 78 matching lines @@
 
     // The used CSS value of column-count, i.e. how many columns there are room for without overflowing.
     unsigned usedColumnCount() const { return multiColumnFlowThread()->columnCount(); }
 
     bool heightIsAuto() const;
 
     // Find the column that contains the given block offset, and return the translation needed to
     // get from flow thread coordinates to visual coordinates.
     LayoutSize flowThreadTranslationAtOffset(LayoutUnit) const;
 
+    LayoutPoint visualPointToFlowThreadPoint(const LayoutPoint& visualPoint) const;
+
     void updateMinimumColumnHeight(LayoutUnit offsetInFlowThread, LayoutUnit height);
 
     // Add a content run, specified by its end position. A content run is appended at every
     // forced/explicit break and at the end of the column set. The content runs are used to
     // determine where implicit/soft breaks will occur, in order to calculate an initial column
     // height.
     void addContentRun(LayoutUnit endOffsetFromFirstPage);
 
     // (Re-)calculate the column height if it's auto. This is first and foremost needed by sets that
     // are to balance the column height, but even when it isn't to be balanced, this is necessary if
@@ skipping 60 matching lines @@
 
     MultiColumnFragmentainerGroupList m_fragmentainerGroups;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutMultiColumnSet, isLayoutMultiColumnSet());
 
 } // namespace blink
 
 #endif // LayoutMultiColumnSet_h