Remove Node.prefix so it's no longer visible to script.

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 0bdbdc5713b91f43c407da3457f82f8d4fc9508a..e4c7260e943245fcdae2b8b56a5014ba8aab438c 100644
--- a/Source/core/dom/Node.h
+++ b/Source/core/dom/Node.h
@@ -206,7 +206,6 @@ public:
     virtual const AtomicString& localName() const;
     virtual const AtomicString& namespaceURI() const;
     virtual const AtomicString& prefix() const;
-    virtual void setPrefix(const AtomicString&, ExceptionState&);
     void normalize();
 
     bool isSameNode(Node* other) const { return this == other; }
@@ -485,7 +484,6 @@ public:
     unsigned childNodeCount() const;
     Node* childNode(unsigned index) const;
 
-    void checkSetPrefix(const AtomicString& prefix, ExceptionState&);
     bool isDescendantOf(const Node*) const;
     bool contains(const Node*) const;
     bool containsIncludingShadowDOM(const Node*) const;
@@ -803,6 +801,8 @@ protected:
     bool isParsingChildrenFinished() const { return getFlag(IsParsingChildrenFinishedFlag); }
     void setIsParsingChildrenFinished(bool value) { setFlag(value, IsParsingChildrenFinishedFlag); }
 
+    void checkSetPrefix(const AtomicString& prefix, ExceptionState&);
+
 private:
     friend class TreeShared<Node>;