cros: Use runtime stylus detection for ash palette.

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

Index: chrome/browser/ui/webui/settings/chromeos/device_stylus_handler.h
diff --git a/chrome/browser/ui/webui/settings/chromeos/device_stylus_handler.h b/chrome/browser/ui/webui/settings/chromeos/device_stylus_handler.h
index c950ffffe6423c6bb9937472d9d2caedc1898f23..a21c40ec6c18ec222bb8ac61c0f821647d2e3e82 100644
--- a/chrome/browser/ui/webui/settings/chromeos/device_stylus_handler.h
+++ b/chrome/browser/ui/webui/settings/chromeos/device_stylus_handler.h
@@ -10,12 +10,19 @@
 #include "base/macros.h"
 #include "chrome/browser/chromeos/note_taking_helper.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 chromeos::NoteTakingHelper::Observer {
+                      public chromeos::NoteTakingHelper::Observer,
+                      public ui::InputDeviceEventObserver {
  public:
   StylusHandler();
   ~StylusHandler() override;
@@ -28,11 +35,19 @@ class StylusHandler : public ::settings::SettingsPageUIHandler,
   // chromeos::NoteTakingHelper::Observer implementation.
   void OnAvailableNoteTakingAppsUpdated() override;
 
+  // ui::InputDeviceObserver:
+  void OnDeviceListsComplete() override;
+
  private:
   void UpdateNoteTakingApps();
   void RequestApps(const base::ListValue* unused_args);
   void SetPreferredNoteTakingApp(const base::ListValue* args);
 
+  // Called by JS to request a |SendHasStylus| call.
+  void HandleInitialize(const base::ListValue* args);
+  // Enables or disables the stylus UI section.
+  void SendHasStylus();
+
   // IDs of available note-taking apps.
   std::set<std::string> note_taking_app_ids_;