[CSS Regions] Elements in a region should be assignable to a named flow

Source/core/dom/ElementRareData.h

Index: Source/core/dom/ElementRareData.h
diff --git a/Source/core/dom/ElementRareData.h b/Source/core/dom/ElementRareData.h
index 84f37adfe9c3e49922ba3bca92435ee9e0820e98..440df8e33239b54d5cb8c00fc1f25f516b15ce54 100644
--- a/Source/core/dom/ElementRareData.h
+++ b/Source/core/dom/ElementRareData.h
@@ -63,6 +63,9 @@ public:
     bool isInCanvasSubtree() const { return m_isInCanvasSubtree; }
     void setIsInCanvasSubtree(bool value) { m_isInCanvasSubtree = value; }
 
+    bool isInsideRegion() const { return m_isInsideRegion; }
+    void setIsInsideRegion(bool value) { m_isInsideRegion = value; }
+
     RegionOversetState regionOversetState() const { return m_regionOversetState; }
     void setRegionOversetState(RegionOversetState state) { m_regionOversetState = state; }
 
@@ -166,6 +169,7 @@ private:
     unsigned m_childrenAffectedByForwardPositionalRules : 1;
     unsigned m_childrenAffectedByBackwardPositionalRules : 1;
 
+    unsigned m_isInsideRegion : 1;
     RegionOversetState m_regionOversetState;
 
     LayoutSize m_minimumSizeForResizing;
@@ -211,6 +215,7 @@ inline ElementRareData::ElementRareData(RenderObject* renderer)
     , m_childrenAffectedByDirectAdjacentRules(false)
     , m_childrenAffectedByForwardPositionalRules(false)
     , m_childrenAffectedByBackwardPositionalRules(false)
+    , m_isInsideRegion(false)
     , m_regionOversetState(RegionUndefined)
     , m_minimumSizeForResizing(defaultMinimumSizeForResizing())
 {