Hide Night Light behind a flag

ash/system/tray/system_tray.cc

 // Copyright (c) 2012 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 "ash/system/tray/system_tray.h"
 
 #include <algorithm>
 #include <map>
 #include <vector>
 
@@ skipping 247 matching lines @@
   AddTrayItem(base::WrapUnique(screen_capture_tray_item_));
   screen_share_tray_item_ = new ScreenShareTrayItem(this);
   AddTrayItem(base::WrapUnique(screen_share_tray_item_));
   AddTrayItem(base::MakeUnique<MultiProfileMediaTrayItem>(this));
   tray_audio_ = new TrayAudio(this);
   AddTrayItem(base::WrapUnique(tray_audio_));
   tray_scale_ = new TrayScale(this);
   AddTrayItem(base::WrapUnique(tray_scale_));
   AddTrayItem(base::MakeUnique<TrayBrightness>(this));
   AddTrayItem(base::MakeUnique<TrayCapsLock>(this));
-  tray_night_light_ = new TrayNightLight(this);
-  AddTrayItem(base::WrapUnique(tray_night_light_));
+  if (NightLightController::IsFeatureEnabled()) {
+    tray_night_light_ = new TrayNightLight(this);
+    AddTrayItem(base::WrapUnique(tray_night_light_));
+  }
   // TODO(jamescook): Remove this when mash has support for display management
   // and we have a DisplayManager equivalent. See http://crbug.com/548429
   if (Shell::GetAshConfig() != Config::MASH)
     AddTrayItem(base::MakeUnique<TrayRotationLock>(this));
   tray_update_ = new TrayUpdate(this);
   AddTrayItem(base::WrapUnique(tray_update_));
   tray_tiles_ = new TrayTiles(this);
   AddTrayItem(base::WrapUnique(tray_tiles_));
   tray_system_info_ = new TraySystemInfo(this);
   AddTrayItem(base::WrapUnique(tray_system_info_));
@@ skipping 419 matching lines @@
           .work_area()
           .height();
   if (work_area_height > 0) {
     UMA_HISTOGRAM_CUSTOM_COUNTS(
         "Ash.SystemMenu.PercentageOfWorkAreaHeightCoveredByMenu",
         100 * bubble_view->height() / work_area_height, 1, 300, 100);
   }
 }
 
 }  // namespace ash