Do not activate system tray bubble by default

ash/common/system/date/date_view.h

 // 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.
 
 #ifndef ASH_COMMON_SYSTEM_DATE_DATE_VIEW_H_
 #define ASH_COMMON_SYSTEM_DATE_DATE_VIEW_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
@@ skipping 21 matching lines @@
  public:
   ~BaseDateTimeView() override;
 
   // Updates the displayed text for the current time and calls SetTimer().
   void UpdateText();
 
   // views::View overrides:
   void GetAccessibleState(ui::AXViewState* state) override;
 
  protected:
-  BaseDateTimeView();
+  explicit BaseDateTimeView(SystemTrayItem* owner);
 
   // Updates labels to display the current time.
   virtual void UpdateTextInternal(const base::Time& now);
 
   // Time format (12/24hr) used for accessibility string.
   base::HourClockType hour_type_;
 
  private:
   // Starts |timer_| to schedule the next update.
   void SetTimer(const base::Time& now);
 
   // Overridden from views::View.
   void ChildPreferredSizeChanged(views::View* child) override;
   void OnLocaleChanged() override;
 
   // Invokes UpdateText() when the displayed time should change.
   base::OneShotTimer timer_;
 
   DISALLOW_COPY_AND_ASSIGN(BaseDateTimeView);
 };
 
 // Popup view used to display the date and day of week.
 class ASH_EXPORT DateView : public BaseDateTimeView {
  public:
-  DateView();
+  explicit DateView(SystemTrayItem* owner);
   ~DateView() override;
 
   // Sets the action the view should take. An actionable date view gives visual
   // feedback on hover, can be focused by keyboard, and clicking/pressing space
   // or enter on the view executes the action.
   void SetAction(TrayDate::DateAction action);
 
   // Updates the format of the displayed time.
   void UpdateTimeFormat();
 
@@ skipping 59 matching lines @@
   std::unique_ptr<views::Label> vertical_label_hours_;
   std::unique_ptr<views::Label> vertical_label_minutes_;
 
   DISALLOW_COPY_AND_ASSIGN(TimeView);
 };
 
 }  // namespace tray
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_DATE_DATE_VIEW_H_