Examine source code of preview select string

{
  "manifest_version": 2,
  "version": "1.1resigned1",
  "name": "preview select string",
  "description": "Add pre tag and indent to selected strings.",
  "permissions": [
    "menus"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "app.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{86f3ab83-acea-4367-acee-6e0de93bf751}"
    }
  }
}