Remove some pre-md code and assets.

ash/common/system/tray/system_tray.cc

Index: ash/common/system/tray/system_tray.cc
diff --git a/ash/common/system/tray/system_tray.cc b/ash/common/system/tray/system_tray.cc
index fa71896f95a43a8c93ba7be0c24180d51b42f1de..de02c98752309b8e365459cfe82f3f69cf26061e 100644
--- a/ash/common/system/tray/system_tray.cc
+++ b/ash/common/system/tray/system_tray.cc
@@ -27,7 +27,6 @@
 #include "ash/common/system/chromeos/screen_security/screen_capture_tray_item.h"
 #include "ash/common/system/chromeos/screen_security/screen_share_tray_item.h"
 #include "ash/common/system/chromeos/session/tray_session_length_limit.h"
-#include "ash/common/system/chromeos/settings/tray_settings.h"
 #include "ash/common/system/chromeos/supervised/tray_supervised_user.h"
 #include "ash/common/system/chromeos/tray_caps_lock.h"
 #include "ash/common/system/chromeos/tray_tracing.h"
@@ -309,8 +308,6 @@ void SystemTray::CreateItems(SystemTrayDelegate* delegate) {
       delegate->CreateRotationLockTrayItem(this);
   if (tray_rotation_lock)
     AddTrayItem(std::move(tray_rotation_lock));
-  if (!use_md)
-    AddTrayItem(base::MakeUnique<TraySettings>(this));
   AddTrayItem(base::WrapUnique(tray_update_));
   if (use_md) {
     tray_tiles_ = new TrayTiles(this);