Considering the impact on privacy, we should aim for having all data cleaners inside ClearDataService properly unit tested.

The current tests are located here: https://searchfox.org/mozilla-central/source/toolkit/components/cleardata/tests/unit

Currently we only need unit/xpcshell tests, though there may be cases where a browser chrome mochitest is required in the future.

Now a checklist:

• ☑️ Cookies
• ☑️ Network Cache
• ⬜️ Image Cache
• ⬜️ Plugin Data (sounds hard)
• ☑️ Downloads
• ☑️ Passwords
• ⬜️ Media Devices
• ⬜️ AppCache
• ⬜️ DOM/Quota Storage
• ⬜️ Predictor network data
• ⬜️ DOM Push Notifications
• ⬜️ Places History
• ⬜️ Session History
• ⬜️ Auth Tokens
• ⬜️ Auth Cache
• ☑️ Permissions
• ☑️ Storage Permission
• ⬜️ Content Prefs
• ⬜️ Secure Site Settings
• ⬜️ EME
• ⬜️ Reporting API reports

Phew. This will certainly keep us busy.