[ash-md] Adds support for Z-order iteration in views::View

ui/views/view.h

Index: ui/views/view.h
diff --git a/ui/views/view.h b/ui/views/view.h
index ab258061984d61ffd373069e7e4ad0f2ea8fab85..71b1cd9c27ace30ac6e407754dcb914d9716dd90 100644
--- a/ui/views/view.h
+++ b/ui/views/view.h
@@ -192,6 +192,8 @@ class VIEWS_EXPORT View : public ui::LayerDelegate,
   void RemoveAllChildViews(bool delete_children);
 
   int child_count() const { return static_cast<int>(children_.size()); }
+  // See also |GetChildrenInZOrder()| below that returns |children_|
+  // in reverse z-order.
   bool has_children() const { return !children_.empty(); }
 
   // Returns the child view at |index|.
@@ -308,6 +310,14 @@ class VIEWS_EXPORT View : public ui::LayerDelegate,
   // Returns whether the view is enabled.
   bool enabled() const { return enabled_; }
 
+  // Returns the child views ordered in reverse z-order. That is, views later in
+  // the returned vector have a higher z-order (are painted later) than those
+  // early in the vector. The returned vector has exactly the same number of
+  // Views as |children_|. The default implementation returns |children_|,
+  // subclass if the paint order should differ from that of |children_|.
+  // This order is taken into account by painting and targeting implementations.
+  virtual View::Views GetChildrenInZOrder();
+
   // Transformations -----------------------------------------------------------
 
   // Methods for setting transformations for a view (e.g. rotation, scaling).