[New Multicolumn] Let a spanner's containing block be the multicol container.

Source/core/rendering/RenderBox.h

Index: Source/core/rendering/RenderBox.h
diff --git a/Source/core/rendering/RenderBox.h b/Source/core/rendering/RenderBox.h
index ff5d6876b98df8e9ae4e4ae68eee0837fa82e92f..a06eeecee31e76256c64e059dbfb5893407bb77c 100644
--- a/Source/core/rendering/RenderBox.h
+++ b/Source/core/rendering/RenderBox.h
@@ -30,6 +30,8 @@
 
 namespace blink {
 
+class RenderMultiColumnSpannerPlaceholder;
+
 struct PaintInfo;
 
 enum SizeType { MainOrPreferredSize, MinSize, MaxSize };
@@ -49,6 +51,7 @@ struct RenderBoxRareData {
 public:
     RenderBoxRareData()
         : m_inlineBoxWrapper(0)
+        , m_spannerPlaceholder(0)
         , m_overrideLogicalContentHeight(-1)
         , m_overrideLogicalContentWidth(-1)
         , m_previousBorderBoxSize(-1, -1)
@@ -58,6 +61,9 @@ public:
     // For inline replaced elements, the inline box that owns us.
     InlineBox* m_inlineBoxWrapper;
 
+    // For spanners, the spanner placeholder that lays us out within the multicol container.
+    RenderMultiColumnSpannerPlaceholder* m_spannerPlaceholder;
+
     LayoutUnit m_overrideLogicalContentHeight;
     LayoutUnit m_overrideLogicalContentWidth;
 
@@ -396,6 +402,9 @@ public:
     void setInlineBoxWrapper(InlineBox*);
     void deleteLineBoxWrapper();
 
+    void setSpannerPlaceholder(RenderMultiColumnSpannerPlaceholder*);
+    virtual RenderMultiColumnSpannerPlaceholder* spannerPlaceholder() const override final { return m_rareData ? m_rareData->m_spannerPlaceholder : 0; }

[Julien - ping for review, 2014/12/11 19:09:37]

We just put final per
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/sjotlpNyF-8

[mstensho (USE GERRIT), 2014/12/11 21:01:14]

Done.

+
     virtual LayoutRect clippedOverflowRectForPaintInvalidation(const RenderLayerModelObject* paintInvalidationContainer, const PaintInvalidationState* = 0) const override;
     virtual void mapRectToPaintInvalidationBacking(const RenderLayerModelObject* paintInvalidationContainer, LayoutRect&, const PaintInvalidationState*) const override;
     virtual void invalidatePaintForOverhangingFloats(bool paintAllDescendants);
@@ -653,9 +662,9 @@ public:
 
     void setIntrinsicContentLogicalHeight(LayoutUnit intrinsicContentLogicalHeight) const { m_intrinsicContentLogicalHeight = intrinsicContentLogicalHeight; }
 protected:
+    virtual void willBeRemovedFromTree() override;
     virtual void willBeDestroyed() override;
 
-
     virtual void styleWillChange(StyleDifference, const RenderStyle& newStyle) override;
     virtual void styleDidChange(StyleDifference, const RenderStyle* oldStyle) override;
     virtual void updateFromStyle() override;