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

Source/core/dom/Node.cpp

Index: Source/core/dom/Node.cpp
diff --git a/Source/core/dom/Node.cpp b/Source/core/dom/Node.cpp
index 896f74f5cad2491b46240c88894dc382ad0c2494..8864f302044d26b7bf34ac108341bd8706c5ac29 100644
--- a/Source/core/dom/Node.cpp
+++ b/Source/core/dom/Node.cpp
@@ -517,14 +517,6 @@ const AtomicString& Node::prefix() const
     return nullAtom;
 }
 
-void Node::setPrefix(const AtomicString& /*prefix*/, ExceptionState& exceptionState)
-{
-    // The spec says that for nodes other than elements and attributes, prefix is always null.
-    // It does not say what to do when the user tries to set the prefix on another type of
-    // node, however Mozilla throws a NamespaceError exception.
-    exceptionState.throwDOMException(NamespaceError, "Prefixes are only supported on element and attribute nodes.");
-}
-
 const AtomicString& Node::localName() const
 {
     return nullAtom;