Do not activate system tray bubble by default

ash/common/system/tray_accessibility.cc

 // 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.
 
 #include "ash/common/system/tray_accessibility.h"
 
 #include "ash/common/accessibility_delegate.h"
 #include "ash/common/accessibility_types.h"
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/session/session_state_delegate.h"
@@ skipping 273 matching lines @@
   }
 }
 
 void AccessibilityDetailedView::HandleButtonPressed(views::Button* sender,
                                                     const ui::Event& event) {
   SystemTrayDelegate* tray_delegate = WmShell::Get()->system_tray_delegate();
   if (sender == help_view_)
     tray_delegate->ShowAccessibilityHelp();
   else if (sender == settings_view_)
     tray_delegate->ShowAccessibilitySettings();
+  else
+    return;
+  owner()->system_tray()->CloseSystemBubble();
 }
 
 }  // namespace tray
 
 ////////////////////////////////////////////////////////////////////////////////
 // ash::TrayAccessibility
 
 TrayAccessibility::TrayAccessibility(SystemTray* system_tray)
     : TrayImageItem(system_tray,
                     IDR_AURA_UBER_TRAY_ACCESSIBILITY,
@@ skipping 111 matching lines @@
     if (detailed_popup_)
       detailed_popup_->GetWidget()->Close();
     if (detailed_menu_)
       detailed_menu_->GetWidget()->Close();
   }
 
   previous_accessibility_state_ = accessibility_state;
 }
 
 }  // namespace ash