Examine source code of Game Timer

{
  "manifest_version": 2,
  "name": "Game Timer",
  "version": "1.0",
  "description": "Track your game playtime.",
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{9524b55c-8294-479a-87d5-520d8b0eebe7}"
    }
  }
}