Examine source code of Timerify

{
  "name": "Timerify",
  "version": "1.0.1",
  "description": "Mind your online time",
  "manifest_version": 2,
  "icons": {
    "48": "icons/timerify-48.png"
  },
  "background": {
    "scripts": [
      "timerify.js"
    ]
  },
  "page_action": {
    "default_icon": "icons/timerify.svg",
    "browser_style": true
  },
  "permissions": [
    "activeTab",
    "tabs",
    "theme"
  ]
}