Do not activate system tray bubble by default

ash/common/system/tray/tray_item_more.h

Index: ash/common/system/tray/tray_item_more.h
diff --git a/ash/common/system/tray/tray_item_more.h b/ash/common/system/tray/tray_item_more.h
index acd9b30a6b729354140f07d94da14388b5ba2347..9a255bdeeaa453df4c869523a65f623192ba76f4 100644
--- a/ash/common/system/tray/tray_item_more.h
+++ b/ash/common/system/tray/tray_item_more.h
@@ -25,8 +25,6 @@ class TrayItemMore : public ActionableView {
   TrayItemMore(SystemTrayItem* owner, bool show_more);
   ~TrayItemMore() override;
 
-  SystemTrayItem* owner() const { return owner_; }
-
   void SetLabel(const base::string16& label);
   void SetImage(const gfx::ImageSkia& image_skia);
   void SetAccessibleName(const base::string16& name);
@@ -44,7 +42,6 @@ class TrayItemMore : public ActionableView {
   void GetAccessibleState(ui::AXViewState* state) override;
   void OnNativeThemeChanged(const ui::NativeTheme* theme) override;
 
-  SystemTrayItem* owner_;
   // True if |more_| should be shown.
   bool show_more_;
   views::ImageView* icon_;