Do not activate system tray bubble by default

ash/common/system/audio/volume_view.h

 // Copyright 2014 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.
 
 #ifndef ASH_COMMON_SYSTEM_AUDIO_VOLUME_VIEW_H_
 #define ASH_COMMON_SYSTEM_AUDIO_VOLUME_VIEW_H_
 
 #include "ash/common/system/tray/actionable_view.h"
 #include "base/macros.h"
 #include "ui/gfx/font.h"
@@ skipping 47 matching lines @@
                           float old_value,
                           views::SliderChangeReason reason) override;
 
   // Overriden from ActionableView.
   bool PerformAction(const ui::Event& event) override;
 
   // views::View:
   void OnBoundsChanged(const gfx::Rect& previous_bounds) override;
   void GetAccessibleState(ui::AXViewState* state) override;
 
-  SystemTrayItem* owner_;
   system::TrayAudioDelegate* audio_delegate_;
   views::View* more_region_;
   VolumeButton* icon_;
   views::Slider* slider_;
   views::Separator* separator_;
   views::ImageView* device_type_;
   views::ImageView* more_;
   bool is_default_view_;
 
   DISALLOW_COPY_AND_ASSIGN(VolumeView);
 };
 
 }  // namespace tray
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_AUDIO_VOLUME_VIEW_H_