Fixed (hopefully) linux build bustage by re-writing the expression w/ a temp variable

layout/xul/base/src/nsTreeRowGroupFrame.cpp

@@ -498,9 +498,10 @@ void
 nsTreeRowGroupFrame::SetScrollbarFrame(nsIFrame* aFrame)
 {
   mScrollbar = aFrame;
+  nsFrameList frameList(mScrollbar);
   
   // Place it in its own list.
-  mScrollbarList.AppendFrames(this, nsFrameList(mScrollbar));
+  mScrollbarList.AppendFrames(this,frameList);
 
   nsCOMPtr<nsIContent> scrollbarContent;
   aFrame->GetContent(getter_AddRefs(scrollbarContent));
@@ -1008,4 +1009,4 @@ void nsTreeRowGroupFrame::CreateScrollbar(nsIPresContext& aPresContext)
                                                &aResult, PR_FALSE, PR_TRUE);
 
   }
-}
+}