Remove CSS regions support, keeping a bare minimum to support "region-based" multicol.

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 908347e5244ead9c9dd7bde209446438b64f4121..084929d318981f64e79afb29a75be7d25de02b1a 100644
--- a/Source/core/dom/Node.h
+++ b/Source/core/dom/Node.h
@@ -265,11 +265,8 @@ public:
     bool isShadowRoot() const { return isDocumentFragment() && isTreeScope(); }
     bool isInsertionPoint() const { return getFlag(IsInsertionPointFlag); }
 
-    bool inNamedFlow() const { return getFlag(InNamedFlowFlag); }
     bool hasCustomStyleCallbacks() const { return getFlag(HasCustomStyleCallbacksFlag); }
 
-    bool isRegisteredWithNamedFlow() const;
-
     bool hasSyntheticAttrChildNodes() const { return getFlag(HasSyntheticAttrChildNodesFlag); }
     void setHasSyntheticAttrChildNodes(bool flag) { setFlag(flag, HasSyntheticAttrChildNodesFlag); }
 
@@ -384,9 +381,6 @@ public:
 
     void setIsLink(bool f);
 
-    void setInNamedFlow() { setFlag(InNamedFlowFlag); }
-    void clearInNamedFlow() { clearFlag(InNamedFlowFlag); }
-
     bool hasScopedHTMLStyleChild() const { return getFlag(HasScopedHTMLStyleChildFlag); }
     void setHasScopedHTMLStyleChild(bool flag) { setFlag(flag, HasScopedHTMLStyleChildFlag); }
 
@@ -708,27 +702,26 @@ private:
 
         HasNameOrIsEditingTextFlag = 1 << 17,
 
-        InNamedFlowFlag = 1 << 18,
-        HasSyntheticAttrChildNodesFlag = 1 << 19,
-        HasCustomStyleCallbacksFlag = 1 << 20,
-        HasScopedHTMLStyleChildFlag = 1 << 21,
-        HasEventTargetDataFlag = 1 << 22,
-        V8CollectableDuringMinorGCFlag = 1 << 23,
-        IsInsertionPointFlag = 1 << 24,
-        IsInShadowTreeFlag = 1 << 25,
+        HasSyntheticAttrChildNodesFlag = 1 << 18,
+        HasCustomStyleCallbacksFlag = 1 << 19,
+        HasScopedHTMLStyleChildFlag = 1 << 20,
+        HasEventTargetDataFlag = 1 << 21,
+        V8CollectableDuringMinorGCFlag = 1 << 22,
+        IsInsertionPointFlag = 1 << 23,
+        IsInShadowTreeFlag = 1 << 24,
 
-        NotifyRendererWithIdenticalStyles = 1 << 26,
+        NotifyRendererWithIdenticalStyles = 1 << 25,
 
-        CustomElement = 1 << 27,
-        CustomElementUpgraded = 1 << 28,
+        CustomElement = 1 << 26,
+        CustomElementUpgraded = 1 << 27,
 
-        ChildNeedsStyleInvalidation = 1 << 29,
-        NeedsStyleInvalidation = 1 << 30,
+        ChildNeedsStyleInvalidation = 1 << 28,
+        NeedsStyleInvalidation = 1 << 29,
 
         DefaultNodeFlags = IsFinishedParsingChildrenFlag | ChildNeedsStyleRecalcFlag | NeedsReattachStyleChange
     };
 
-    // 2 bits remaining.
+    // 3 bits remaining.
 
     bool getFlag(NodeFlags mask) const { return m_nodeFlags & mask; }
     void setFlag(bool f, NodeFlags mask) const { m_nodeFlags = (m_nodeFlags & ~mask) | (-(int32_t)f & mask); }