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

Source/core/dom/Node.h

Index: Source/core/dom/Node.h
diff --git a/Source/core/dom/Node.h b/Source/core/dom/Node.h
index 72b32b3808a87b6d810816538c717a8d6fb97551..957b8394257da3380b2d06e44b3b721fac46812d 100644
--- a/Source/core/dom/Node.h
+++ b/Source/core/dom/Node.h
@@ -57,6 +57,7 @@ class EventContext;
 class EventDispatchMediator;
 class EventListener;
 class FloatPoint;
+class FlowThreadController;
 class Frame;
 class HTMLInputElement;
 class IntRect;
@@ -270,6 +271,8 @@ public:
     bool inNamedFlow() const { return getFlag(InNamedFlowFlag); }
     bool hasCustomStyleCallbacks() const { return getFlag(HasCustomStyleCallbacksFlag); }
 
+    bool isRegisteredWithNamedFlow(const FlowThreadController*) const;
+
     bool hasSyntheticAttrChildNodes() const { return getFlag(HasSyntheticAttrChildNodesFlag); }
     void setHasSyntheticAttrChildNodes(bool flag) { setFlag(flag, HasSyntheticAttrChildNodesFlag); }