[New Multicolumn] Actual support for layout of column-span:all.

Source/core/rendering/RenderMultiColumnFlowThread.h

Index: Source/core/rendering/RenderMultiColumnFlowThread.h
diff --git a/Source/core/rendering/RenderMultiColumnFlowThread.h b/Source/core/rendering/RenderMultiColumnFlowThread.h
index 3e02d85e10e5c5a21010871cdeb0d26625581e8d..c3adb8783bd6a036ff6fe65fa0fa1469a7977e1d 100644
--- a/Source/core/rendering/RenderMultiColumnFlowThread.h
+++ b/Source/core/rendering/RenderMultiColumnFlowThread.h
@@ -122,7 +122,6 @@ public:
     unsigned columnCount() const { return m_columnCount; }
     LayoutUnit columnHeightAvailable() const { return m_columnHeightAvailable; }
     void setColumnHeightAvailable(LayoutUnit available) { m_columnHeightAvailable = available; }
-    virtual bool heightIsAuto() const { return !columnHeightAvailable() || multiColumnBlockFlow()->style()->columnFill() == ColumnFillBalance; }
     bool progressionIsInline() const { return m_progressionIsInline; }
 
     virtual LayoutSize columnOffset(const LayoutPoint&) const override final;
@@ -149,6 +148,10 @@ private:
     virtual const char* renderName() const override;
     virtual void addRegionToThread(RenderMultiColumnSet*) override;
     virtual void willBeRemovedFromTree() override;
+    virtual bool isColumnSpanner(const RenderObject*) const override;
+    virtual bool isInsideColumnSpanner(const RenderObject*) const override final;
+    virtual LayoutUnit enterColumnSpannerBeforeLayout(RenderBox*, LayoutUnit logicalTop, SubtreeLayoutScope&) override;
+    virtual void leaveColumnSpannerAfterLayout(RenderBox*, LayoutUnit logicalBottom) override;
     virtual void flowThreadDescendantWasInserted(RenderObject*) override;
     virtual void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues&) const override;
     virtual void updateLogicalWidth() override;
@@ -161,6 +164,11 @@ private:
     typedef HashMap<const RenderObject*, RenderMultiColumnSpannerSet*> SpannerMap;
     SpannerMap m_spannerMap;
 
+    // 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.