Examine source code of Just The Calendar

{
  "manifest_version": 2,
  "name": "Just The Calendar",
  "version": "0.1.1resigned1",
  "description": "Just the Facebook Calendar",
  "homepage_url": "https://www.justthecalendar.com",
  "icons": {
    "48": "icons/JustTheCal48.png"
  },
  "permissions": [
    "activeTab"
  ],
  "optional_permissions": [
    "*://connect.facebook.net/*",
    "webRequest"
  ],
  "browser_action": {
    "default_icon": "icons/JustTheCal32.png",
    "default_title": "Just The Calendar",
    "default_popup": "popup/justthecal.html"
  },
  "web_accessible_resources": [
    "images/JustTheCalendar_image1.jpg"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{fb2f9cfd-dc89-4a7d-89ff-1d0a14407a1b}"
    }
  }
}