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

Source/core/rendering/RenderMultiColumnSpannerSet.cpp

Index: Source/core/rendering/RenderMultiColumnSpannerSet.cpp
diff --git a/Source/core/rendering/RenderMultiColumnSpannerSet.cpp b/Source/core/rendering/RenderMultiColumnSpannerSet.cpp
index 69ae4f36398f84e73fb69e9fb029b7a511a12baf..d41b8b757de9777dcfb1be198c47b9f7c7fe6765 100644
--- a/Source/core/rendering/RenderMultiColumnSpannerSet.cpp
+++ b/Source/core/rendering/RenderMultiColumnSpannerSet.cpp
@@ -28,6 +28,18 @@ bool RenderMultiColumnSpannerSet::recalculateColumnHeight(BalancedHeightCalculat
     return false;
 }
 
+void RenderMultiColumnSpannerSet::computeLogicalHeight(LayoutUnit, LayoutUnit logicalTop, LogicalExtentComputedValues& computedValues) const
+{
+    computedValues.m_extent = m_rendererInFlowThread->logicalHeight();
+    computedValues.m_position = logicalTop;
+}
+
+LayoutUnit RenderMultiColumnSpannerSet::pageLogicalHeight() const
+{
+    ASSERT(!m_rendererInFlowThread->needsLayout());
+    return m_rendererInFlowThread->logicalHeight();

[Julien - ping for review, 2014/12/03 23:02:22]

Isn't there an issue here if we don't have enough room for the content and thus
should fall back to the non-spanning case?

[mstensho (USE GERRIT), 2014/12/10 13:48:19]

Talking about "When space is limited, it may be impossible to find room for the
spanning element. In these cases, user agents may treat the element as if none
had been specified on this property."?

http://dev.w3.org/csswg/css-multicol/#column-span

Yeah, we won't implement that. In the current implementation that would mean
that we would have to modify the render tree structure dynamically, based on
actual layout, which is just evil (and also verboten in Blink). I've been
fighting with Håkon to get that removed from the spec. :)

+}
+
 const char* RenderMultiColumnSpannerSet::renderName() const
 {
     return "RenderMultiColumnSpannerSet";