Examine source code of Ravicon

{
  "manifest_version": 2,
  "name": "Ravicon",
  "version": "0.1.0",
  "description": "Generates an identicon using Ravatar based on the host of the current web page.",
  "icons": {
    "512": "icons/512.png"
  },
  "page_action": {},
  "background": {
    "page": "background.html"
  },
  "permissions": [
    "tabs"
  ]
}