Enable options to remap CapsLock whenever an external keyboard is connected.

chrome/browser/ui/webui/options/chromeos/keyboard_handler.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 CHROME_BROWSER_UI_WEBUI_OPTIONS_CHROMEOS_KEYBOARD_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_OPTIONS_CHROMEOS_KEYBOARD_HANDLER_H_
 
 #include "base/compiler_specific.h"
 #include "base/prefs/pref_member.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
+#include "ui/events/devices/input_device_event_observer.h"
 
 namespace chromeos {
 namespace options {
 
 // Customize modifier keys overlay page UI handler.
-class KeyboardHandler : public ::options::OptionsPageUIHandler {
+class KeyboardHandler
+    : public ::options::OptionsPageUIHandler,
+      public ui::InputDeviceEventObserver {
  public:
   KeyboardHandler();
   ~KeyboardHandler() override;
 
   // OptionsPageUIHandler implementation.
   void GetLocalizedValues(base::DictionaryValue* localized_strings) override;
   void InitializePage() override;
   void RegisterMessages() override;
 
+  // ui::InputDeviceEventObserver:
+  void OnKeyboardDeviceConfigurationChanged() override;
+
  private:
   // Show the keyboard shortcuts overlay from the options page.
   void HandleShowKeyboardShortcuts(const base::ListValue* args);
 
+  // Shows or hides the CapsLock options based on whether or not there is an
+  // external keyboard connected.
+  void UpdateCapsLockOptions() const;
+
   DISALLOW_COPY_AND_ASSIGN(KeyboardHandler);
 };
 
 }  // namespace options
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_UI_WEBUI_OPTIONS_CHROMEOS_KEYBOARD_HANDLER_H_