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

Source/core/rendering/LayoutState.cpp

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 #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"
 #include "platform/Partitions.h"
 
 namespace blink {
 
 LayoutState::LayoutState(LayoutUnit pageLogicalHeight, bool pageLogicalHeightChanged, RenderView& view)
     : m_isPaginated(pageLogicalHeight)
     , m_pageLogicalHeightChanged(pageLogicalHeightChanged)
@@ skipping 42 matching lines @@
         // If we don't establish a new page height, then propagate the old page height and offset down.
         m_pageLogicalHeight = m_next->m_pageLogicalHeight;
         m_pageLogicalHeightChanged = m_next->m_pageLogicalHeightChanged;
         m_pageOffset = m_next->m_pageOffset;
 
         // Disable pagination for objects we don't support. For now this includes overflow:scroll/auto, inline blocks and
         // writing mode roots.
         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;
         }
     }
 
     if (!m_columnInfo)
         m_columnInfo = m_next->m_columnInfo;
 
     // FIXME: <http://bugs.webkit.org/show_bug.cgi?id=13443> Apply control clip if present.
 }
 
 LayoutState::LayoutState(RenderObject& root)
@@ skipping 41 matching lines @@
 }
 
 void LayoutState::addForcedColumnBreak(const RenderBox& child, const LayoutUnit& childLogicalOffset)
 {
     if (!m_columnInfo || m_columnInfo->columnHeight())
         return;
     m_columnInfo->addForcedBreak(pageLogicalOffset(child, childLogicalOffset));
 }
 
 } // namespace blink