Do not activate system tray bubble by default

ui/views/bubble/tray_bubble_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 UI_VIEWS_BUBBLE_TRAY_BUBBLE_VIEW_H_
 #define UI_VIEWS_BUBBLE_TRAY_BUBBLE_VIEW_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 136 matching lines @@
 
   // Called when the delegate is destroyed.
   void reset_delegate() { delegate_ = NULL; }
 
   Delegate* delegate() { return delegate_; }
 
   void set_gesture_dragging(bool dragging) { is_gesture_dragging_ = dragging; }
   bool is_gesture_dragging() const { return is_gesture_dragging_; }
 
   // Overridden from views::WidgetDelegate.
-  bool CanActivate() const override;
   views::NonClientFrameView* CreateNonClientFrameView(
       views::Widget* widget) override;
   bool WidgetHasHitTestMask() const override;
   void GetWidgetHitTestMask(gfx::Path* mask) const override;
 
   // Overridden from views::BubbleDialogDelegateView.
   gfx::Rect GetAnchorRect() const override;
   void OnBeforeBubbleWidgetInit(Widget::InitParams* params,
                                 Widget* bubble_widget) const override;
 
@@ skipping 39 matching lines @@
 
   // Used to find any mouse movements.
   std::unique_ptr<MouseWatcher> mouse_watcher_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayBubbleView);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_BUBBLE_TRAY_BUBBLE_VIEW_H_