Examine source code of Video Speed 2x

{
  "manifest_version": 2,
  "name": "Video Speed Booster",
  "version": "1.0.1",
  "description": "ワンクリックで動画の再生速度を2倍にします",
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "browser_action": {
    "default_icon": {
      "16": "icon-16.png",
      "32": "icon-32.png",
      "48": "icon-48.png"
    },
    "default_title": "2倍速"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "16": "icon-16.png",
    "32": "icon-32.png",
    "48": "icon-48.png",
    "64": "icon-64.png",
    "96": "icon-96.png",
    "128": "icon-128.png",
    "256": "icon-256.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{91f73750-e69d-4c9b-b155-aca85c802016}"
    }
  }
}