Change "struct" to "class ... { public:" to quiet a warning.

git-svn-id: svn://10.0.0.236/trunk@64061 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/layout/html/base/src/nsFrameManager.cpp

@@ -83,7 +83,8 @@ protected:
 
 MOZ_DECL_CTOR_COUNTER(UndisplayedNode);
 
-struct UndisplayedNode {
+class UndisplayedNode {
+public:
   UndisplayedNode(nsIContent* aContent, nsIStyleContext* aStyle)
   {
     MOZ_COUNT_CTOR(UndisplayedNode);