Examine source code of Custom Homepage

{
  "manifest_version": 2,
  "name": "Custom Homepage",
  "version": "1.0",
  "description": "Customize your browser homepage",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "popup.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{63d6aac7-5b38-475d-9436-f04ddae90595}"
    }
  }
}