Bug 1650245 Part 1 - Move begin() and end() into private section in CSSOrderAwareFrameIterator. r=dholbert

Both methods are implementation details specific to this iterator, not
public interfaces that can be cooperated with C++ standard library, so
move them into private section.

Differential Revision: https://phabricator.services.mozilla.com/D82117

layout/generic/CSSOrderAwareFrameIterator.h

@@ -125,8 +125,6 @@ class CSSOrderAwareFrameIteratorT {
   }
 
   bool IsForward() const;
-  Iterator begin(const nsFrameList& aList);
-  Iterator end(const nsFrameList& aList);
 
   nsIFrame* operator*() const {
     MOZ_ASSERT(!AtEnd());
@@ -241,6 +239,9 @@ class CSSOrderAwareFrameIteratorT {
                                            nsIFrame* const& b);
 
  private:
+  Iterator begin(const nsFrameList& aList);
+  Iterator end(const nsFrameList& aList);
+
   nsFrameList mChildren;
   // Used if child list is already in ascending 'order'.
   Maybe<Iterator> mIter;