HttpOnly, secure cookie with clearCookies: false are cleared when I close the app

I'am using this package for display a website with a cookies that doesn't expire when the browser is closed (the app in this case). The cookie has httpOnly and secure flags, every time that I close the app they are cleared. I set clearCookies = false (default value) but it doesn't works

## System info

Issue occurs on: Android, not tested on iOS
Plugin version: 0.3.11
Flutter doctor output:

```
Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, 1.22.2, on Microsoft Windows [Versione 10.0.18363.1139], locale it-IT)

[√] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
[!] Android Studio (version 4.1.0)
X Flutter plugin not installed; this adds Flutter specific functionality.
X Dart plugin not installed; this adds Dart specific functionality.
[√] VS Code (version 1.51.0)
[!] Connected device
! No devices available
```

まず、HttpOnly で secure な Cookie と clearCookies=false を使用し、Android 上で plugin version 0.3.11 によりこれを再現します。Issue ではソースファイルもテストも指定されていません。アプリを終了して再度開いた後も Cookie が残ることを確認できれば完了です。プロジェクトに関連するテスト場所が用意されている場合は、回帰テストのカバレッジも追加します。

索引モデルが issue の本文から書いたものです。