Signin screen and locked screen status area focus advancing

ash/common/system/status_area_widget_delegate.h

Index: ash/common/system/status_area_widget_delegate.h
diff --git a/ash/common/system/status_area_widget_delegate.h b/ash/common/system/status_area_widget_delegate.h
index 915bff9017d27677aafc2ac72b666216e9ad6782..d7b7fe86b4b4d027e6177561110eb5749f2fb5ea 100644
--- a/ash/common/system/status_area_widget_delegate.h
+++ b/ash/common/system/status_area_widget_delegate.h
@@ -33,8 +33,20 @@ class ASH_EXPORT StatusAreaWidgetDelegate : public views::AccessiblePaneView,
 
   void set_alignment(ShelfAlignment alignment) { alignment_ = alignment; }
 
+  void set_custom_focus_traversable(
+      views::FocusTraversable* custom_focus_traversable) {
+    custom_focus_traversable_ = custom_focus_traversable;
+  }
+
+  void set_default_last_focusable_child(bool default_last_focusable_child) {
+    default_last_focusable_child_ = default_last_focusable_child;
+  }
+
   // Overridden from views::AccessiblePaneView.
   View* GetDefaultFocusableChild() override;
+  views::FocusSearch* GetFocusSearch() override;
+  views::FocusTraversable* GetFocusTraversableParent() override;
+  views::View* GetFocusTraversableParentView() override;
 
   // Overridden from views::View:
   views::Widget* GetWidget() override;
@@ -60,6 +72,12 @@ class ASH_EXPORT StatusAreaWidgetDelegate : public views::AccessiblePaneView,
   // screen.
   void SetBorderOnChild(views::View* child, bool extend_border_to_edge);
 
+  views::FocusTraversable* custom_focus_traversable_ = nullptr;
+
+  // When true, the default focus of the status area widget is the last
+  // focusable child.
+  bool default_last_focusable_child_ = false;
+
   const FocusCycler* focus_cycler_for_testing_;
 
   // TODO(jamescook): Get this from WmShelf.