Examine source code of History Filter

{
  "manifest_version": 2,
  "name": "History Filter",
  "version": "1.1.0",
  "description": "Removes matching sites from Firefox history as soon as they are visited.",
  "icons": {
    "16": "icons/icon-16.png",
    "19": "icons/icon-19.png",
    "32": "icons/icon-32.png",
    "38": "icons/icon-38.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "permissions": [
    "activeTab",
    "history",
    "storage"
  ],
  "background": {
    "scripts": [
      "matcher.js",
      "settings.js",
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "History Filter",
    "default_icon": {
      "16": "icons/icon-16.png",
      "32": "icons/icon-32.png"
    },
    "default_popup": "options.html"
  },
  "page_action": {
    "default_title": "History Filter",
    "default_icon": {
      "19": "icons/page-on-19.png",
      "38": "icons/page-on-38.png"
    }
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8a1bbb52-41ca-4d64-969a-dd0814803435}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}