Stop using shell::GetInstance()->system_tray() in system tray items

ash/system/brightness/tray_brightness.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/brightness/tray_brightness.h"
 
 #include "ash/accelerators/accelerator_controller.h"
 #include "ash/ash_constants.h"
 #include "ash/shell.h"
 #include "ash/system/brightness/brightness_control_delegate.h"
@@ skipping 106 matching lines @@
   bool dragging_;
 
   // Last brightness level that we observed, in the range [0.0, 100.0].
   double last_percent_;
 
   DISALLOW_COPY_AND_ASSIGN(BrightnessView);
 };
 
 }  // namespace tray
 
-TrayBrightness::TrayBrightness()
-    : weak_ptr_factory_(this),
+TrayBrightness::TrayBrightness(SystemTray* system_tray)
+    : SystemTrayItem(system_tray),
+      weak_ptr_factory_(this),
       brightness_view_(NULL),
       is_default_view_(false),
       current_percent_(100.0),
       got_current_percent_(false) {
   // Post a task to get the initial brightness; the BrightnessControlDelegate
   // isn't created yet.
   MessageLoopForUI::current()->PostTask(
       FROM_HERE,
       base::Bind(&TrayBrightness::GetInitialBrightness,
                  weak_ptr_factory_.GetWeakPtr()));
@@ skipping 63 matching lines @@
     return;
 
   if (brightness_view_)
     SetDetailedViewCloseDelay(kTrayPopupAutoCloseDelayInSeconds);
   else
     PopupDetailedView(kTrayPopupAutoCloseDelayInSeconds, false);
 }
 
 }  // namespace internal
 }  // namespace ash