[Firefox] Make use of the webext-specific API to clear localStorage and indexedDB

[gorhill]

Excerpt from https://blog.mozilla.org/addons/2017/11/20/extensions-in-firefox-58/:

The browsingData API now supports clearing the indexedDB storage area The browsingData API supports clearing localStorage by hostname, similar to cookies

Currently uMatrix uses a content script to try to clear localStorage as per cookie cell, while it does not touch indexedDB storage due to missing API to enumerate databases.

[mikhaelkh]

Are storages being cleared in Chrome? I unchecked all hosts files, purged all caches. Storage used didn't decrease and stayed at ~3.3MB.

[zero77]

Yes, It would be nice to have control over allowing or blocking indexedDB storage throw the popup panel and auto clearing of indexedDB storage, if that’s what you were thinking.

Also, I think this API will be supported from the 23rd in the main FF release. https://wiki.mozilla.org/RapidRelease/Calendar

[zero77]

This may not currently be possible in chrome but it should work well in FF. https://bugs.chromium.org/p/chromium/issues/detail?id=78093