diff -r 000000000000 -r 6474c204b198 layout/xul/nsStackLayout.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/xul/nsStackLayout.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,56 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+
+  Eric D Vaughan
+  A frame that can have multiple children. Only one child may be displayed at one time. So the
+  can be flipped though like a deck of cards.
+ 
+**/
+
+#ifndef nsStackLayout_h___
+#define nsStackLayout_h___
+
+#include "mozilla/Attributes.h"
+#include "nsBoxLayout.h"
+#include "nsCOMPtr.h"
+#include "nsCoord.h"
+
+class nsIPresShell;
+
+nsresult NS_NewStackLayout(nsIPresShell* aPresShell, nsCOMPtr<nsBoxLayout>& aNewLayout);
+
+class nsStackLayout : public nsBoxLayout
+{
+public:
+
+  friend nsresult NS_NewStackLayout(nsIPresShell* aPresShell, nsCOMPtr<nsBoxLayout>& aNewLayout);
+  static void Shutdown();
+
+  nsStackLayout();
+
+  NS_IMETHOD Layout(nsIFrame* aBox, nsBoxLayoutState& aState) MOZ_OVERRIDE;
+
+  virtual nsSize GetPrefSize(nsIFrame* aBox, nsBoxLayoutState& aBoxLayoutState) MOZ_OVERRIDE;
+  virtual nsSize GetMinSize(nsIFrame* aBox, nsBoxLayoutState& aBoxLayoutState) MOZ_OVERRIDE;
+  virtual nsSize GetMaxSize(nsIFrame* aBox, nsBoxLayoutState& aBoxLayoutState) MOZ_OVERRIDE;
+  virtual nscoord GetAscent(nsIFrame* aBox, nsBoxLayoutState& aBoxLayoutState) MOZ_OVERRIDE;
+
+  // get the child offsets for aChild and set them in aMargin. Returns a
+  // bitfield mask of the SPECIFIED_LEFT, SPECIFIED_RIGHT, SPECIFIED_TOP and
+  // SPECIFIED_BOTTOM offsets indicating which sides have been specified by
+  // attributes.
+  static uint8_t GetOffset(nsBoxLayoutState& aState, nsIFrame* aChild, nsMargin& aMargin);
+
+private:
+  static nsBoxLayout* gInstance;
+
+}; // class nsStackLayout
+
+
+
+#endif
+