Examine source code of Ctrl + A (Select All)

{
  "content_scripts": [
    {
      "js": [
        "jquery.min.js",
        "run.js"
      ],
      "matches": [
        "https://tweetdeck.twitter.com/*"
      ],
      "run_at": "document_end"
    }
  ],
  "description": "Add a button to RT with with all teamed accounts even with the new TweetDeck update that restricts users to one account per retweet",
  "manifest_version": 2,
  "name": "Ctrl + A (Select All)",
  "permissions": [
    "*://*/*"
  ],
  "update_url": "https://clients2.google.com/service/update2/crx",
  "version": "1.6resigned1",
  "applications": {
    "gecko": {
      "id": "llkhmcjkflajcgioljbamhcepjgpgibj@chrome-store-foxified-unsigned"
    }
  }
}