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

Source/core/rendering/LayoutState.cpp

Index: Source/core/rendering/LayoutState.cpp
diff --git a/Source/core/rendering/LayoutState.cpp b/Source/core/rendering/LayoutState.cpp
index 5a2ba588c863af8ff9a30ec37a578a713a38d08b..93537dae40703f79264b375f7dec82711770e6fd 100644
--- a/Source/core/rendering/LayoutState.cpp
+++ b/Source/core/rendering/LayoutState.cpp
@@ -26,6 +26,7 @@
 #include "config.h"
 #include "core/rendering/LayoutState.h"
 
+#include "core/rendering/RenderFlowThread.h"
 #include "core/rendering/RenderInline.h"
 #include "core/rendering/RenderLayer.h"
 #include "core/rendering/RenderView.h"
@@ -88,8 +89,12 @@ LayoutState::LayoutState(RenderBox& renderer, const LayoutSize& offset, LayoutUn
         if (renderer.isUnsplittableForPagination()) {
             m_pageLogicalHeight = 0;
             m_isPaginated = false;
+        } else if (RenderFlowThread* flowThread = renderer.flowThreadContainingBlock()) {
+            // FIXME: this won't do if/when we add support for nested fragmentation contexts (e.g. a
+            // multicol container inside something paginated).

[Julien - ping for review, 2014/09/30 00:39:32]

This seems like a big limitation of this patch. I assume this matches the
current code but I would like that explicitly mentioned.

[mstensho (USE GERRIT), 2014/09/30 20:20:28]

Done. More comment.

This patch doesn't introduce this limitation, though. It just relies on it. :)

+            m_isPaginated = !flowThread->isInsideColumnSpanner(&renderer);
         } else {
-            m_isPaginated = m_pageLogicalHeight || m_next->m_columnInfo || renderer.flowThreadContainingBlock();
+            m_isPaginated = m_pageLogicalHeight || m_next->m_columnInfo;
         }
     }