cros: Use runtime stylus detection for ash palette.

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

+// 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.
+
+#include "chrome/browser/ui/webui/settings/chromeos/device_stylus_handler.h"
+
+#include "ash/common/system/chromeos/palette/palette_utils.h"
+#include "base/bind.h"
+#include "ui/events/devices/input_device_manager.h"
+
+namespace chromeos {
+namespace settings {
+
+StylusHandler::StylusHandler() {
+  ui::InputDeviceManager::GetInstance()->AddObserver(this);
+}
+
+StylusHandler::~StylusHandler() {
+  ui::InputDeviceManager::GetInstance()->RemoveObserver(this);
+}
+
+void StylusHandler::RegisterMessages() {
+  web_ui()->RegisterMessageCallback(
+      "initializeStylusSettings",
+      base::Bind(&StylusHandler::HandleInitialize, base::Unretained(this)));
+}
+
+void StylusHandler::OnJavascriptAllowed() {}
+
+void StylusHandler::OnJavascriptDisallowed() {}
+
+void StylusHandler::OnDeviceListsComplete() {
+  SendHasStylus();
+}
+
+void StylusHandler::HandleInitialize(const base::ListValue* args) {
+  AllowJavascript();
+  if (ui::InputDeviceManager::GetInstance()->AreDeviceListsComplete())
+    SendHasStylus();
+}
+
+void StylusHandler::SendHasStylus() {
+  DCHECK(ui::InputDeviceManager::GetInstance()->AreDeviceListsComplete());
+  CallJavascriptFunction("cr.webUIListenerCallback",
+                         base::StringValue("has-stylus-changed"),
+                         base::FundamentalValue(ash::HasStylusInput()));
+}
+
+}  // namespace settings
+}  // namespace chromeos