Makes DefaultContainerLayoutManager ignore windows with transient

ui/aura/window.h

Index: ui/aura/window.h
diff --git a/ui/aura/window.h b/ui/aura/window.h
index 2554716188537780875d6fc28c467c69424f7b96..8a9b0306e265862afb9eacfbfdd19926dd907736 100644
--- a/ui/aura/window.h
+++ b/ui/aura/window.h
@@ -182,6 +182,11 @@ class AURA_EXPORT Window : public ui::LayerDelegate {
   void AddTransientChild(Window* child);
   void RemoveTransientChild(Window* child);
 
+  const Windows& transient_children() const { return transient_children_; }
+
+  Window* transient_parent() { return transient_parent_; }
+  const Window* transient_parent() const { return transient_parent_; }
+
   // Retrieves the first-level child with the specified id, or NULL if no first-
   // level child is found matching |id|.
   Window* GetChildById(int id);