"Storage used" in settings tab says "? bytes"

[yasmise]

Describe the issue

In uBlock Origin 1.13.9.0, "Storage used" in settings tab says "? bytes", as shown in a screenshot below. Stable (1.13.8) says correct value.

One or more specific URLs where the issue occurs

moz-extension://1926ce9b-fc7f-4e3c-b002-048c0f16ae31/dashboard.html#settings.html

Screenshot in which the issue can be seen

Steps for anyone to reproduce the issue

1. Open "Dashboard" of uBlock Origin and go to "Settings" tab.
2. "Storage used" doesn't say correct value.

Your settings

• OS/version: Windows 10 Home 1703
• Browser/version: Firefox 54.0.1 64bit
• uBlock Origin version: 1.13.9.0

I can reproduce this with a clean Firefox profile. Only uBlock Origin is installed.

Your filter lists

Default filter lists + JPN

Your custom filters (if any)

Nothing

[gorhill]

browser.storage.local.getBytesInUse() is not supported by Firefox's WebExtensions API: https://developer.mozilla.org/en-US/Add-ons/WebExtensions/API/storage/StorageArea/getBytesInUse#Browser_compatibility.

[uBlock-user]

Issue still exists in FF 57 Nightly.

Do they have any plans of adding it ?

[yasmise]

FYI, Bugzilla's URL is here.
https://bugzilla.mozilla.org/show_bug.cgi?id=1385832