Examine source code of Digital Clock

{
  "manifest_version" : 2 ,
  "name" : "Digital Clock",
  "description" : "A digital clock for the browser",
  "version" : "1.2",
  "default_locale" : "en" ,
  "browser_action" : {
    "default_popup" : "options.html"
  },
  "background" : {
    "page": "background.html"
  },
  "permissions" : [
    "storage" 
  ]
}