Examine source code of Water Clock

{
  "background": {
    "persistent": false,
    "page": "background.html"
  },
  "chrome_url_overrides": {
    "newtab": "index.html"
  },
  "default_locale": "en",
  "description": "__MSG_app_description__",
  "icons": {
    "16": "images/16.png",
    "32": "images/32.png",
    "48": "images/48.png",
    "64": "images/64.png",
    "128": "images/128.png"
  },
  "manifest_version": 2,
  "name": "__MSG_app_name__",
  "permissions": [],
  "short_name": "WaterClock",
  "version": "2.2.3"
}