[New Multicolumn] Support for paged overflow. (By mstensho).

Source/core/rendering/RenderBlockFlow.h

Index: Source/core/rendering/RenderBlockFlow.h
diff --git a/Source/core/rendering/RenderBlockFlow.h b/Source/core/rendering/RenderBlockFlow.h
index 6c52afaa07c006ae2063b13f1d14bb56e6fd4fc3..1c77a074c2737aba5c19754a684393a65fd7267a 100644
--- a/Source/core/rendering/RenderBlockFlow.h
+++ b/Source/core/rendering/RenderBlockFlow.h
@@ -291,7 +291,18 @@ private:
 
     virtual RootInlineBox* createRootInlineBox(); // Subclassed by SVG
 
-    void createOrDestroyMultiColumnFlowThreadIfNeeded();
+    bool isPagedOverflow(const RenderStyle*);
+
+    enum FlowThreadType {
+        NoFlowThread,
+        MultiColumnFlowThread,
+        PagedFlowThread
+    };
+
+    FlowThreadType flowThreadType(const RenderStyle*);
+
+    RenderMultiColumnFlowThread* createMultiColumnFlowThread(FlowThreadType);
+    void createOrDestroyMultiColumnFlowThreadIfNeeded(const RenderStyle* oldStyle);
 
     void updateLogicalWidthForAlignment(const ETextAlign&, const RootInlineBox*, BidiRun* trailingSpaceRun, float& logicalLeft, float& totalLogicalWidth, float& availableLogicalWidth, unsigned expansionOpportunityCount);
     void checkForPaginationLogicalHeightChange(LayoutUnit& pageLogicalHeight, bool& pageLogicalHeightChanged, bool& hasSpecifiedPageLogicalHeight);