Remove status icon if there are no more notifications.

chrome/browser/ui/views/message_center/web_notification_tray.cc

Index: chrome/browser/ui/views/message_center/web_notification_tray.cc
diff --git a/chrome/browser/ui/views/message_center/web_notification_tray.cc b/chrome/browser/ui/views/message_center/web_notification_tray.cc
index 473468cffe7f5c5049a5c9f91c0c34dd731ab459..bcb19192c4d59bc1899808a48e3efd20c3914499 100644
--- a/chrome/browser/ui/views/message_center/web_notification_tray.cc
+++ b/chrome/browser/ui/views/message_center/web_notification_tray.cc
@@ -276,6 +276,11 @@ void WebNotificationTray::UpdateStatusIcon() {
     tool_tip = l10n_util::GetStringUTF16(IDS_MESSAGE_CENTER_TOOLTIP);
   }
 
+  if (message_center()->GetVisibleNotifications().empty()) {
+    DestroyStatusIcon();
+    return;
+  }
+
   gfx::ImageSkia* icon_image = GetIcon(
       unread_notifications,
       message_center()->IsQuietMode());