Don't pass NodeBuffer as Seq[Node]

Author: lrytz

shared/src/main/scala/scala/xml/Document.scala

@@ -36,7 +36,7 @@ class Document extends NodeSeq with Serializable {
    *  excluded. If there is a document type declaration, the list also
    *  contains a document type declaration information item.
    */
-  var children: Seq[Node] = _
+  var children: Seq[Node] = _ // effectively an `immutable.Seq`, not changed due to binary compatibility
 
   /** The element information item corresponding to the document element. */
   var docElem: Node = _

shared/src/main/scala/scala/xml/Utility.scala

@@ -354,6 +354,7 @@ object Utility extends AnyRef with parsing.TokenTests {
     null
   }
 
+  // unused, untested
   def parseAttributeValue(value: String): Seq[Node] = {
     val sb: StringBuilder = new StringBuilder
     var rfb: StringBuilder = null
@@ -398,7 +399,7 @@ object Utility extends AnyRef with parsing.TokenTests {
       else
         nb += x
     }
-    nb
+    nb.toVector
   }
 
   /**

shared/src/main/scala/scala/xml/parsing/MarkupParser.scala

@@ -242,7 +242,7 @@ trait MarkupParser extends MarkupParserCommon with TokenTests {
     }
 
     nextch() // is prolog ?
-    var children: NodeSeq = null
+    var children: Seq[Node] = null
     if ('?' == ch) {
       nextch()
       info_prolog = prolog()
@@ -255,7 +255,7 @@ trait MarkupParser extends MarkupParserCommon with TokenTests {
       val ts: NodeBuffer = new NodeBuffer()
       content1(TopScope, ts) // DTD handled as side effect
       ts &+ content(TopScope)
-      children = NodeSeq.fromSeq(ts)
+      children = ts.toVector
     }
     //println("[MarkupParser::document] children now: "+children.toList)
     var elemCount: Int = 0
@@ -451,8 +451,7 @@ trait MarkupParser extends MarkupParserCommon with TokenTests {
   def content(pscope: NamespaceBinding): NodeSeq = {
     val ts: NodeBuffer = new NodeBuffer
     var exit: Boolean = eof
-    // todo: optimize seq repr.
-    def done: NodeSeq = NodeSeq.fromSeq(ts.toList)
+    def done: NodeSeq = NodeSeq.fromSeq(ts.toVector)
 
     while (!exit) {
       tmppos = pos