Examine source code of ShowOnMap

{
  "manifest_version": 2,
  "name": "ShowOnMap",
  "description": "Opens GoogleMaps in new Tab with selected content as search text.",
  "version": "1.1resigned1",
  "icons": {
    "48": "icons/location-48.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "activeTab",
    "contextMenus"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{e3751b50-8bdb-4eb9-8213-fa7e259a25cd}"
    }
  }
}