Examine source code of Youtube Watch Counter

{
  "manifest_version": 2,
  "name": "Youtube Watch Counter",
  "version": "1.1.1",
  "description": "Counts how many times you have watched a video on youtube. And how much time you have watched it.",
  "permissions": [
    "https://www.youtube.com/*",
    "storage",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/*"
      ],
      "js": [
        "main.js"
      ],
      "run_at": "document_end"
    }
  ],
  "browser_action": {
    "default_title": "Youtube Watch Counter",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "youtubewatchcounter@walcriz.net"
    }
  }
}