Examine source code of Memory Hole

{
  "manifest_version": 2,
  "name": "Memory Hole",
  "version": "1.1",
  "description": "Periodically delete history and cookies older than some threshold.",
  "browser_action": {
    "default_popup": "popup.html"
  },
  "permissions": [
    "history",
    "cookies",
    "storage",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{38e1204b-5e68-4745-a86f-915284e7c948}"
    }
  }
}