Calculate minimum column height after layout.

third_party/WebKit/Source/core/layout/ColumnBalancer.h

Index: third_party/WebKit/Source/core/layout/ColumnBalancer.h
diff --git a/third_party/WebKit/Source/core/layout/ColumnBalancer.h b/third_party/WebKit/Source/core/layout/ColumnBalancer.h
index daab0d98ec96bf2fa2d591bd0191efcfb0430c54..ffa74005d729b4faad8b3c94247124e947df82c4 100644
--- a/third_party/WebKit/Source/core/layout/ColumnBalancer.h
+++ b/third_party/WebKit/Source/core/layout/ColumnBalancer.h
@@ -38,7 +38,7 @@ protected:
 
     // Examine and collect column balancing data from a line that has been found to intersect with
     // this fragmentainer group. Does not recurse into layout objects on that line.
-    virtual void examineLine(const RootInlineBox&) = 0;
+    virtual void examineLine(const LayoutBlockFlow& containingBlock, const RootInlineBox&) = 0;
 
     // Examine and collect column balancing data for everything in the fragmentainer group. Will
     // trigger calls to examineBoxAfterEntering(), examineBoxBeforeLeaving() and examineLine() for
@@ -74,7 +74,7 @@ private:
 
     void examineBoxAfterEntering(const LayoutBox&);
     void examineBoxBeforeLeaving(const LayoutBox&);
-    void examineLine(const RootInlineBox&);
+    void examineLine(const LayoutBlockFlow& containingBlock, const RootInlineBox&);

[leviw_travelin_and_unemployed, 2015/11/05 18:44:26]

Since we're only looking at RootInlineBoxes, the containing block is always
accessible via the block() method on RootInlineBlock in O(1) time. Splitting the
object off seems more error prone to me.

[mstensho (USE GERRIT), 2015/11/05 19:15:56]

I was unsure, with the ongoing efforts to untangle line layout from LayoutObject
in mind. But if I'm not introducing any unwanted coupling by doing it, I'll do
it. :)

[mstensho (USE GERRIT), 2015/11/05 22:17:10]

Done.

 
     // Record that there's a pagination strut that ends at the specified |offsetInFlowThread|, which
     // is an offset exactly at the top of some column.
@@ -138,6 +138,8 @@ private:
     //
     // [1] http://www.w3.org/TR/css3-break/#parallel-flows
     Vector<LayoutUnit, 32> m_shortestStruts;
+
+    LayoutUnit m_minimumColumnLogicalHeight;
 };
 
 // If we have previously used InitialColumnHeightFinder to estimate an initial column height, and
@@ -154,7 +156,7 @@ public:
 private:
     void examineBoxAfterEntering(const LayoutBox&);
     void examineBoxBeforeLeaving(const LayoutBox&);
-    void examineLine(const RootInlineBox&);
+    void examineLine(const LayoutBlockFlow& containingBlock, const RootInlineBox&);
 
     void recordSpaceShortage(LayoutUnit shortage)
     {