Examine source code of Google PDF Viewer

{
  "description": "Allows you to view pdf files with the google pdf viewer.",
  "manifest_version": 2,
  "name": "Google PDF Viewer",
  "version": "1.3.7.6resigned1",
  "default_locale": "en",
  "applications": {
    "gecko": {
      "id": "{b734ba68-4cab-41e0-9141-9f8d00373d93}",
      "strict_min_version": "54.0"
    }
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "*://*/*",
    "tabs",
    "contextMenus",
    "downloads"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://docs.google.com/viewer?url=*&pdf=true",
        "https://docs.google.com/viewerng/viewer?url=*&pdf=true"
      ],
      "js": [
        "viewer.js"
      ],
      "run_at": "document_start"
    },
    {
      "matches": [
        "*://*/*"
      ],
      "exclude_matches": [
        "https://docs.google.com/*",
        "https://content.googleapis.com/*",
        "https://clients6.google.com/*",
        "https://accounts.google.com/*",
        "https://*.googleusercontent.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start",
      "all_frames": true
    }
  ]
}