Give up focus if the focused view becomes unfocusable

ui/views/focus/focus_manager.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_VIEWS_FOCUS_FOCUS_MANAGER_H_
 #define UI_VIEWS_FOCUS_FOCUS_MANAGER_H_
 
 #include <list>
 #include <map>
 
@@ skipping 166 matching lines @@
 
   // Get the reason why the focus most recently changed.
   FocusChangeReason focus_change_reason() const {
     return focus_change_reason_;
   }
 
   // Clears the focused view. The window associated with the top root view gets
   // 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();
 
   // Stores the focused view. Used when the widget loses activation.
   // |clear_native_focus| indicates whether this should invoke ClearFocus().
   // Typically |true| should be passed in.
   void StoreFocusedView(bool clear_native_focus);
 
   // Restore the view saved with a previous call to StoreFocusedView(). Used
@@ skipping 175 matching lines @@
 
   // See description above getter.
   bool is_changing_focus_;
 
   DISALLOW_COPY_AND_ASSIGN(FocusManager);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_FOCUS_FOCUS_MANAGER_H_