Examine source code of TagCheck

{
  "manifest_version": 2,
  "name": "TagCheck",
  "version": "1.0",
  "description": "Check for Google Analytics on a page.",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "embeddedthemba@gmail.com"
    }
  },
  "browser_action": {
    "default_icon": "icons/icon-96.png",
    "default_title": "TagCheck",
    "default_popup": "popup/tagcheck.html"
  }
}