Change system settings based on when mouse/touchpad is connected/disconnected.

chrome/browser/ui/webui/options/chromeos/system_options_handler.h

 // Copyright (c) 2011 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_SYSTEM_OPTIONS_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_OPTIONS_CHROMEOS_SYSTEM_OPTIONS_HANDLER_H_
 #pragma once
 
 #include "base/memory/weak_ptr.h"
 #include "base/compiler_specific.h"
+#include "chrome/browser/chromeos/device_hierarchy_observer.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
 
 namespace base {
 class DictionaryValue;
 }
 
 // ChromeOS system options page UI handler.
 class SystemOptionsHandler
   : public OptionsPageUIHandler,
+    public chromeos::DeviceHierarchyObserver,
     public base::SupportsWeakPtr<SystemOptionsHandler> {
  public:
   SystemOptionsHandler();
   virtual ~SystemOptionsHandler();
 
   // OptionsPageUIHandler implementation.
   virtual void GetLocalizedValues(
       base::DictionaryValue* localized_strings) OVERRIDE;
   virtual void Initialize() OVERRIDE;
 
   virtual void RegisterMessages() OVERRIDE;
 
+  // DeviceHierarchyObserver implementation.
+  virtual void DeviceHierarchyChanged() OVERRIDE;
+
   // Called when the accessibility checkbox value is changed.
   // |args| will contain the checkbox checked state as a string
   // ("true" or "false").
   void AccessibilityChangeCallback(const base::ListValue* args);
 
   // Called when the System configuration screen is used to adjust
   // the screen brightness.
   // |args| will be an empty list.
   void DecreaseScreenBrightnessCallback(const base::ListValue* args);
   void IncreaseScreenBrightnessCallback(const base::ListValue* args);
 
  private:
-  // Callback for TouchpadHelper.
+  // Check for input devices.
+  void CheckTouchpadExists();
+  void CheckMouseExists();
+
+  // Callback for input device checks.
   void TouchpadExists(bool* exists);
+  void MouseExists(bool* exists);
 
   DISALLOW_COPY_AND_ASSIGN(SystemOptionsHandler);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_OPTIONS_CHROMEOS_SYSTEM_OPTIONS_HANDLER_H_