Do not activate TrayBubbleView by default

ash/system/web_notification/web_notification_tray.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_SYSTEM_WEB_NOTIFICATION_WEB_NOTIFICATION_TRAY_H_
 #define ASH_SYSTEM_WEB_NOTIFICATION_WEB_NOTIFICATION_TRAY_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
@@ skipping 73 matching lines @@
   void HideBubbleWithView(const views::TrayBubbleView* bubble_view) override;
   void ClickedOutsideBubble() override;
 
   // Overridden from ActionableView.
   bool PerformAction(const ui::Event& event) override;
 
   // Overridden from views::TrayBubbleView::Delegate.
   void BubbleViewDestroyed() override;
   void OnMouseEnteredView() override;
   void OnMouseExitedView() override;
+  void RegisterAccelerators(const std::vector<ui::Accelerator>& accelerators,
+                            views::TrayBubbleView* tray_bubble_view) override;
+  void UnregisterAllAccelerators(
+      views::TrayBubbleView* tray_bubble_view) override;
   base::string16 GetAccessibleNameForBubble() override;
+  bool ShouldEnableExtraKeyboardAccessibility() override;
   void HideBubble(const views::TrayBubbleView* bubble_view) override;
 
   // Overridden from MessageCenterTrayDelegate.
   void OnMessageCenterTrayChanged() override;
   bool ShowMessageCenter() override;
   void HideMessageCenter() override;
   bool ShowPopups() override;
   void HidePopups() override;
   bool ShowNotifierSettings() override;
   bool IsContextMenuEnabled() const override;
@@ skipping 70 matching lines @@
   bool should_block_shelf_auto_hide_;
 
   std::unique_ptr<AshPopupAlignmentDelegate> popup_alignment_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(WebNotificationTray);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_WEB_NOTIFICATION_WEB_NOTIFICATION_TRAY_H_