Examine source code of Track it!

{
  "manifest_version" : 2 ,
  "name" : "__MSG_extName__" ,
  "homepage_url" : "https://github.com/mornir/track-it",
  "default_locale" : "en" ,
  "permissions" : [
    "history" ,
    "storage" 
  ],
  "icons" : {
    "16" : "icons/clock_16.png",
    "32" : "icons/clock_32.png",
    "48" : "icons/clock_48.png",
    "128" : "icons/clock_128.png"
  },
  "browser_action" : {
    "default_popup" : "popup.html",
    "default_title" : "__MSG_extName__" ,
    "default_icon" : {
      "16" : "icons/clock_16.png",
      "32" : "icons/clock_32.png"
    }
  },
  "options_ui" : {
    "page": "options.html" 
  },
  "version" : "0.2.0",
  "description" : "Web extension to track time wasted on addictive websites",
  "content_security_policy" : "script-src 'self' ; object-src 'self'"
}