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

Source/core/rendering/RenderFlowThread.h

Index: Source/core/rendering/RenderFlowThread.h
diff --git a/Source/core/rendering/RenderFlowThread.h b/Source/core/rendering/RenderFlowThread.h
index 74a6b9cb50c34fa38658469ba0c5b208af1935e2..6b773f64fdc8a30c8f0ba52923deb49ca4780160 100644
--- a/Source/core/rendering/RenderFlowThread.h
+++ b/Source/core/rendering/RenderFlowThread.h
@@ -67,6 +67,13 @@ public:
     // can easily avoid drawing the children directly.
     virtual LayerType layerTypeRequired() const override final { return NormalLayer; }
 
+    virtual bool isColumnSpanner(const RenderObject*) const { return false; }
+
+    // Is the specified renderer a column spanner or inside one?
+    virtual bool isInsideColumnSpanner(const RenderObject*) const { return false; }
+
+    virtual LayoutUnit enterColumnSpannerBeforeLayout(RenderBox*, LayoutUnit logicalTop, SubtreeLayoutScope&) { return LayoutUnit(); }
+    virtual void leaveColumnSpannerAfterLayout(RenderBox*, LayoutUnit logicalBottom) { }
     virtual void flowThreadDescendantWasInserted(RenderObject*) { }
 
     virtual bool nodeAtPoint(const HitTestRequest&, HitTestResult&, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction) override final;
@@ -116,14 +123,14 @@ public:
     // Used to estimate the maximum height of the flow thread.
     static LayoutUnit maxLogicalHeight() { return LayoutUnit::max() / 2; }
 
+    virtual RenderMultiColumnSet* columnSetAtBlockOffset(LayoutUnit) const = 0;

[mstensho (USE GERRIT), 2014/11/07 16:06:01]

Note: made this public to be able to write a unit test for it. While it would be
nice to encapsulate RenderMultiColumnSet, so that e.g. RenderBlockFlow doesn't
get tempted to use it, there were already public getters for
RenderMultiColumnSet here, so it doesn't make much of a difference.

+
 protected:
     virtual const char* renderName() const = 0;
 
     void updateRegionsFlowThreadPortionRect();
     bool shouldIssuePaintInvalidations(const LayoutRect&) const;
 
-    virtual RenderMultiColumnSet* columnSetAtBlockOffset(LayoutUnit) const = 0;
-
     bool cachedOffsetFromLogicalTopOfFirstRegion(const RenderBox*, LayoutUnit&) const;
     void setOffsetFromLogicalTopOfFirstRegion(const RenderBox*, LayoutUnit);
     void clearOffsetFromLogicalTopOfFirstRegion(const RenderBox*);
@@ -135,9 +142,9 @@ protected:
     typedef PODInterval<LayoutUnit, RenderMultiColumnSet*> MultiColumnSetInterval;
     typedef PODIntervalTree<LayoutUnit, RenderMultiColumnSet*> MultiColumnSetIntervalTree;
 
-    class RegionSearchAdapter {
+    class MultiColumnSetSearchAdapter {
     public:
-        RegionSearchAdapter(LayoutUnit offset)
+        MultiColumnSetSearchAdapter(LayoutUnit offset)
             : m_offset(offset)
             , m_result(0)
         {
@@ -147,11 +154,11 @@ protected:
         const LayoutUnit& highValue() const { return m_offset; }
         void collectIfNeeded(const MultiColumnSetInterval&);
 
-        RenderRegion* result() const { return m_result; }
+        RenderMultiColumnSet* result() const { return m_result; }
 
     private:
         LayoutUnit m_offset;
-        RenderRegion* m_result;
+        RenderMultiColumnSet* m_result;
     };
 
     // Stack of objects that pushed a LayoutState object on the RenderView. The