Examine source code of GFill

{
  "name": "GFill",
  "short_name": "GF",
  "version": "4.0.2",
  "manifest_version": 2,
  "description": "This extension help to fill information",
  "homepage_url": "https://addons.mozilla.org/en-US/firefox/addon/gfill/",
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "default_locale": "vi",
  "browser_action": {
    "default_icon": "icons/icon20.png",
    "default_title": "GFill",
    "default_popup": "src/popup.html"
  },
  "background": {
    "scripts": [
      "src/background.js"
    ]
  },
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://accounts.google.com/*"
      ],
      "js": [
        "dist/jquery.min.js",
        "src/fill_g.js"
      ],
      "run_at": "document_end",
      "all_frames": true
    },
    {
      "matches": [
        "*://*.mail.ru/*"
      ],
      "js": [
        "dist/jquery.min.js",
        "src/fill_r.js"
      ],
      "run_at": "document_end",
      "all_frames": true
    },
    {
      "matches": [
        "*://infoq.vn/Registers/*"
      ],
      "js": [
        "dist/jquery.min.js",
        "src/fill_i.js"
      ],
      "run_at": "document_end",
      "all_frames": true
    }
  ]
}