cros: Use runtime stylus detection for ash palette.

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

 // Copyright (c) 2016 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_OPTIONS_STYLUS_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_OPTIONS_CHROMEOS_OPTIONS_STYLUS_HANDLER_H_
 
 #include <set>
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/chromeos/note_taking_helper.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
+#include "ui/events/devices/input_device_event_observer.h"
 
 namespace base {
 class ListValue;
 }  // namespace base
 
 namespace chromeos {
 namespace options {
 
 // Stylus-specific options C++ code.
 class OptionsStylusHandler : public ::options::OptionsPageUIHandler,
-                             public NoteTakingHelper::Observer {
+                             public NoteTakingHelper::Observer,
+                             public ui::InputDeviceEventObserver {
  public:
   OptionsStylusHandler();
   ~OptionsStylusHandler() override;
 
   // OptionsPageUIHandler implementation.
   void GetLocalizedValues(base::DictionaryValue* localized_strings) override;
   void InitializePage() override;
   void RegisterMessages() override;
 
   // NoteTakingHelper::Observer implementation.
   void OnAvailableNoteTakingAppsUpdated() override;
 
+  // ui::InputDeviceEventObserver implementation:
+  void OnDeviceListsComplete() override;
+
  private:
+  // Called from WebUI when the page is initialized to determine if stylus
+  // settings should be shown.
+  void RequestStylusHardwareState(const base::ListValue* args);
+
+  // Sends if there is a stylus device to WebUI.
+  void SendHasStylus();
+
   // Updates the note-taking app menu in the stylus overlay to display the
   // currently-available set of apps.
   void UpdateNoteTakingApps();
 
   // Called from WebUI when the user selects a note-taking app.
   void SetPreferredNoteTakingApp(const base::ListValue* args);
 
   // IDs of available note-taking apps.
   std::set<std::string> note_taking_app_ids_;
 
   base::WeakPtrFactory<OptionsStylusHandler> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(OptionsStylusHandler);
 };
 
 }  // namespace options
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_UI_WEBUI_OPTIONS_CHROMEOS_OPTIONS_STYLUS_HANDLER_H_