Examine source code of Documents Scann

{
  "name": "Documents Scann",
  "version": "3.5",
  "manifest_version": 2,
  "minimum_chrome_version": "37",
  "app": {
    "background": {
      "scripts": [
        "background.js"
      ]
    }
  },
  "permissions": [],
  "optional_permissions": [
    "documentScan"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{17b8eb11-f219-40f4-9042-81a3e1022139}"
    }
  }
}