WebExtensions/Applications - MozillaWiki

This article is in parts, or in its entirety, outdated and should be treated with due caution. The browser_specific_settings manifest.json key has replaced the applications key and Fx will prompt a warning (when testing in about:debugging) that applications will be ignored if both are present. For up to date information, visit developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest

[Rockridge]

Chrome拡張機能のマニフェストファイル（manifest.json）を修正しなくてもFirefox上で動かせるようになりそうだ。