Examine source code of Always Preview (obsolete)

{
  "description": "Allows you to preview most pdf files with the pdf reader.",
  "manifest_version": 2,
  "name": "Always Preview",
  "version": "1.8.8resigned1",
  "applications": {
    "gecko": {
      "id": "{b434be68-4cab-41e0-9141-9f8d00373d93}",
      "strict_min_version": "57.0"
    }
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start",
      "all_frames": true
    }
  ]
}