Examine source code of Cert Canary

{
  "manifest_version": 2,
  "name": "Cert Canary",
  "version": "0.2",
  "description": "Warns of pending certificate expiration",
  "icons": {
    "96": "icons/canary96.png"
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "16": "icons/canary16.png",
      "32": "icons/canary32.png"
    },
    "default_title": "Cert Canary",
    "default_popup": "popup/canary.html"
  },
  "permissions": [
    "webNavigation",
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{97777dee-0f73-4acf-b371-96360ab3251e}"
    }
  }
}