Give up focus if the focused view becomes unfocusable

ui/views/focus/focus_manager.h

Index: ui/views/focus/focus_manager.h
diff --git a/ui/views/focus/focus_manager.h b/ui/views/focus/focus_manager.h
index ebdc2a3d88e2034ec7b08359af0546dddb9f07ce..bb62085522f74a588b7827b32f97e3c15fce0dfa 100644
--- a/ui/views/focus/focus_manager.h
+++ b/ui/views/focus/focus_manager.h
@@ -184,6 +184,10 @@ class VIEWS_EXPORT FocusManager {
   // the native focus (so we still get keyboard events).
   void ClearFocus();
 
+  // Tries to advance focus if the focused view has become unfocusable. If there
+  // is no view available to advance focus to, focus will be cleared.
+  void AdvanceFocusIfNecessary();
+
   // Validates the focused view, clearing it if the window it belongs too is not
   // attached to the window hierarchy anymore.
   void ValidateFocusedView();