{
  "prefbar:info": {
    "formatversion": 3
  },
  "prefbar:menu:enabled": {
    "items": [
      "prefbar:button:prefetch-next"
    ]
  },
  "prefbar:button:prefetch-next": {
    "type": "check",
    "label": "先読み",
    "prefstring": "network.prefetch-next",
    "topref": "value",
    "frompref": "value"
  }
}