Examine source code of bookmark.newtab

{
  "manifest_version": 2,
  "name": "bookmark.newtab",
  "version": "1.0.8",
  "developer": {
    "name": "Manuel"
  },
  "description": "Shows a page with a bookmark bar instead of the default tab page",
  "applications": {
    "gecko": {
      "id": "@bookmarknewtab"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "@bookmarknewtab"
    }
  },
  "page_action": {
    "default_title": "Store favicon",
    "default_icon": {
      "19": "ico-19.png",
      "38": "ico-38.png"
    },
    "show_matches": [
      "http://*/*",
      "https://*/*"
    ],
    "pinned": false
  },
  "background": {
    "scripts": [
      "clearClosedTabs.js"
    ]
  },
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "permissions": [
    "sessions",
    "tabs",
    "storage",
    "bookmarks",
    "history"
  ]
}