Examine source code of Link Counter

{
  "name": "Link Counter",
  "version": "1.3resigned1",
  "description": "A simple extension that counts the number of links on the current page.",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "icons": {
    "128": "icon_128.png"
  },
  "permissions": [
    "tabs",
    "http://*/*",
    "https://*/*"
  ],
  "browser_action": {
    "default_title": "Vision Tech Link Counter",
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{453969e8-9039-4f4e-b809-9d2f84c90043}"
    }
  }
}