[New Multicolumn] Add support for column-span:all

Source/core/rendering/RenderMultiColumnSet.h

Index: Source/core/rendering/RenderMultiColumnSet.h
diff --git a/Source/core/rendering/RenderMultiColumnSet.h b/Source/core/rendering/RenderMultiColumnSet.h
index c09e482d166a8f0c834eb36c2c0a78627c40c0c9..ac223b6ae6292501a15c4db3679560ca35589ae9 100644
--- a/Source/core/rendering/RenderMultiColumnSet.h
+++ b/Source/core/rendering/RenderMultiColumnSet.h
@@ -50,7 +50,7 @@ namespace blink {
 //
 // Column spans result in the creation of new column sets, since a spanning renderer has to be
 // placed in between the column sets that come before and after the span.
-class RenderMultiColumnSet FINAL : public RenderRegion {
+class RenderMultiColumnSet : public RenderRegion {
 public:
     enum BalancedHeightCalculation { GuessFromFlowThreadPortion, StretchBySpaceShortage };
 
@@ -59,7 +59,7 @@ public:
     virtual bool isRenderMultiColumnSet() const OVERRIDE { return true; }
 
     virtual LayoutUnit pageLogicalWidth() const OVERRIDE FINAL { return flowThread()->logicalWidth(); }
-    virtual LayoutUnit pageLogicalHeight() const OVERRIDE FINAL { return m_columnHeight; }
+    virtual LayoutUnit pageLogicalHeight() const OVERRIDE { return m_columnHeight; }
 
     RenderBlockFlow* multiColumnBlockFlow() const { return toRenderBlockFlow(parent()); }
     RenderMultiColumnFlowThread* multiColumnFlowThread() const
@@ -71,14 +71,19 @@ public:
     RenderMultiColumnSet* nextSiblingMultiColumnSet() const;
     RenderMultiColumnSet* previousSiblingMultiColumnSet() const;
 
+    void setLogicalTopInFlowThread(LayoutUnit);
     LayoutUnit logicalTopInFlowThread() const { return isHorizontalWritingMode() ? flowThreadPortionRect().y() : flowThreadPortionRect().x(); }
-    LayoutUnit logicalBottomInFlowThread() const { return isHorizontalWritingMode() ? flowThreadPortionRect().maxY() : flowThreadPortionRect().maxX(); }
-
     LayoutUnit logicalHeightInFlowThread() const { return isHorizontalWritingMode() ? flowThreadPortionRect().height() : flowThreadPortionRect().width(); }
+    void setLogicalBottomInFlowThread(LayoutUnit);
+    LayoutUnit logicalBottomInFlowThread() const { return isHorizontalWritingMode() ? flowThreadPortionRect().maxY() : flowThreadPortionRect().maxX(); }
 
     // 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;
+
+    bool requiresBalancing() const { return !isRenderMultiColumnSpannerSet() && heightIsAuto(); }
+
     // 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;
@@ -94,8 +99,10 @@ public:
     // height.
     void addContentRun(LayoutUnit endOffsetFromFirstPage);
 
-    // (Re-)calculate the column height if it's auto.
-    bool recalculateColumnHeight(BalancedHeightCalculation);
+    // (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
+    // the multicol container's height is constrained.
+    virtual bool recalculateColumnHeight(BalancedHeightCalculation);
 
     // Record space shortage (the amount of space that would have been enough to prevent some
     // element from being moved to the next column) at a column break. The smallest amount of space
@@ -106,6 +113,17 @@ public:
     // Reset previously calculated column height. Will mark for layout if needed.
     void resetColumnHeight();
 
+    // Prepare this set for flow thread layout.
+    void resetFlow();
+    // Layout of flow thread content that's to be rendered inside this column set begins. This
+    // happens at the beginning of flow thread layout, and when advancing from a previous column set
+    // or spanner to this one.
+    void beginFlow(LayoutUnit offsetInFlowThread);
+    // Layout of flow thread content that was to be rendered inside this column set has
+    // finished. This happens at end of flow thread layout, and when advancing to the next column
+    // set or spanner.
+    void endFlow(LayoutUnit offsetInFlowThread);
+
     // Expand this set's flow thread portion rectangle to contain all trailing flow thread
     // overflow. Only to be called on the last set.
     void expandToEncompassFlowThreadContentsIfNeeded();
@@ -127,9 +145,10 @@ public:
 
     void collectLayerFragments(LayerFragments&, const LayoutRect& layerBoundingBox, const LayoutRect& dirtyRect);
 
-private:
+protected:
     RenderMultiColumnSet(RenderFlowThread*);
 
+private:
     virtual void insertedIntoTree() OVERRIDE FINAL;
     virtual void willBeRemovedFromTree() OVERRIDE FINAL;
 
@@ -207,6 +226,28 @@ private:
     Vector<ContentRun, 1> m_contentRuns;
 };
 
+inline void RenderMultiColumnSet::resetFlow()
+{
+    // Start with "infinite" flow thread portion height until height is known.
+    setLogicalBottomInFlowThread(RenderFlowThread::maxLogicalHeight());
+}
+
+inline void RenderMultiColumnSet::beginFlow(LayoutUnit offsetInFlowThread)
+{
+    // At this point layout is exactly at the beginning of this set. Store block offset from flow
+    // thread start.
+    setLogicalTopInFlowThread(offsetInFlowThread);
+}
+
+inline void RenderMultiColumnSet::endFlow(LayoutUnit offsetInFlowThread)
+{
+    // At this point layout is exactly at the end of this set. Store block offset from flow thread
+    // start. This set is now considered "flowed", although we may have to revisit it later (with
+    // beginFlow()), e.g. if a subtree in the flow thread has to be laid out over again because the
+    // initial margin collapsing estimates were wrong.
+    setLogicalBottomInFlowThread(offsetInFlowThread);
+}
+
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderMultiColumnSet, isRenderMultiColumnSet());
 
 } // namespace blink