[New Multicolumn] Intrinsic/preferred logical width calculation for spanners.

Source/core/rendering/RenderMultiColumnFlowThread.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 173 matching lines @@
     void createAndInsertMultiColumnSet(RenderBox* insertBefore = 0);
     void createAndInsertSpannerPlaceholder(RenderBox* spanner, RenderBox* insertBefore = 0);
     virtual bool descendantIsValidColumnSpanner(RenderObject* descendant) const;
 
     virtual const char* renderName() const override;
     virtual void addRegionToThread(RenderMultiColumnSet*) override;
     virtual void willBeRemovedFromTree() override;
     virtual LayoutUnit skipColumnSpanner(RenderBox*, LayoutUnit logicalTopInFlowThread) override;
     virtual void flowThreadDescendantWasInserted(RenderObject*) override;
     virtual void flowThreadDescendantWillBeRemoved(RenderObject*) override;
+    virtual void computePreferredLogicalWidths() override;
     virtual void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues&) const override;
     virtual void updateLogicalWidth() override;
     virtual void setPageBreak(LayoutUnit offset, LayoutUnit spaceShortage) override;
     virtual void updateMinimumPageHeight(LayoutUnit offset, LayoutUnit minHeight) override;
     virtual bool addForcedRegionBreak(LayoutUnit, RenderObject* breakChild, bool isBefore, LayoutUnit* offsetBreakAdjustment = 0) override;
     virtual bool isPageLogicalHeightKnown() const override;
 
     // The last set we worked on. It's not to be used as the "current set". The concept of a
     // "current set" is difficult, since layout may jump back and forth in the tree, due to wrong
     // top location estimates (due to e.g. margin collapsing), and possibly for other reasons.
     RenderMultiColumnSet* m_lastSetWorkedOn;
 
     unsigned m_columnCount; // The used value of column-count
     LayoutUnit m_columnHeightAvailable; // Total height available to columns, or 0 if auto.
     bool m_inBalancingPass; // Set when relayouting for column balancing.
     bool m_needsColumnHeightsRecalculation; // Set when we need to recalculate the column set heights after layout.
     bool m_progressionIsInline; // Always true for regular multicol. False for paged-y overflow.
     bool m_isBeingEvacuated;
 };
 
 } // namespace blink
 
 #endif // RenderMultiColumnFlowThread_h