Examine source code of Time Tracker

{
  "name": "Time Tracker",
  "version": "1.0.1.0",
  "description": "Track the time you spend your activities!",
  "permissions": [
    "storage",
    "<all_urls>"
  ],
  "browser_action": {
    "default_popup": "index.html",
    "default_icon": {
      "16": "icon16.png",
      "32": "icon32.png",
      "48": "icon48.png",
      "64": "icon64.png",
      "128": "icon128.png"
    }
  },
  "icons": {
    "16": "icon16.png",
    "32": "icon32.png",
    "48": "icon48.png",
    "64": "icon64.png",
    "128": "icon128.png"
  },
  "manifest_version": 2
}