cros: Use runtime stylus detection for ash palette.

chrome/browser/ui/webui/settings/chromeos/device_stylus_handler.h

+// Copyright 2017 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_SETTINGS_CHROMEOS_DEVICE_STYLUS_HANDLER_H_
+#define CHROME_BROWSER_UI_WEBUI_SETTINGS_CHROMEOS_DEVICE_STYLUS_HANDLER_H_
+
+#include "base/macros.h"
+#include "chrome/browser/ui/webui/settings/settings_page_ui_handler.h"
+#include "ui/events/devices/input_device_event_observer.h"
+
+namespace base {
+class ListValue;
+}
+
+namespace chromeos {
+namespace settings {
+
+// Chrome OS stylus settings handler.
+class StylusHandler : public ::settings::SettingsPageUIHandler,
+                      public ui::InputDeviceEventObserver {
+ public:
+  StylusHandler();
+  ~StylusHandler() override;
+
+  // SettingsPageUIHandler implementation.
+  void RegisterMessages() override;
+  void OnJavascriptAllowed() override;
+  void OnJavascriptDisallowed() override;
+
+ private:
+  // ui::InputDeviceObserver:
+  void OnDeviceListsComplete() override;
+
+  // Called by JS to request a |SendHasStylus| call.
+  void HandleInitialize(const base::ListValue* args);
+
+  // Enables or disables the stylus UI section.
+  void SendHasStylus();
+
+  DISALLOW_COPY_AND_ASSIGN(StylusHandler);
+};
+
+}  // namespace settings
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_CHROMEOS_DEVICE_STYLUS_HANDLER_H_