Examine source code of ImageSlotMachine

{
  "manifest_version": 2,
  "name": "ImageSlotMachine",
  "version": "1.0",
  "description": "Turn images into slot machines: click to cycle randomly through images from the same source.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "slotmachine.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{4c9a9ea9-8106-4643-b0e2-7b5a16dc6979}"
    }
  }
}