Show the unread button even without any unread notifications

ui/message_center/message_center_tray.cc

 // Copyright (c) 2013 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 "ui/message_center/message_center_tray.h"
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/observer_list.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 240 matching lines @@
 
 void MessageCenterTray::OnQuietModeChanged(bool in_quiet_mode) {
   NotifyMessageCenterTrayChanged();
 }
 
 void MessageCenterTray::OnBlockingStateChanged(NotificationBlocker* blocker) {
   OnMessageCenterChanged();
 }
 
 void MessageCenterTray::OnMessageCenterChanged() {
-  if (message_center_visible_ && message_center_->NotificationCount() == 0)
-    HideMessageCenterBubble();

[dewittj, 2016/05/09 16:27:52]

This change isn't reflected in the CL description - it look like it leaves the
message center open even after every notification is gone.  Is that intended?

[yoshiki, 2016/05/10 03:52:07]

I thought it was intended. But per PM discussion, we don't need to do it.

-
   if (popups_visible_ && !message_center_->HasPopupNotifications())
     HidePopupBubbleInternal();
   else if (!popups_visible_ && message_center_->HasPopupNotifications())
     ShowPopupBubble();
 
   NotifyMessageCenterTrayChanged();
 }
 
 void MessageCenterTray::NotifyMessageCenterTrayChanged() {
   delegate_->OnMessageCenterTrayChanged();
 }
 
 }  // namespace message_center