Examine source code of Topsites

{
  "manifest_version": 2,
  "name": "Topsites",
  "short_name": "Most visited websites",
  "version": "1.0",
  "description": "Most visited websites",
  "icons": {
    "16": "images/Icon-16.png",
    "48": "images/Icon-48.png",
    "128": "images/Icon-128.png"
  },
  "permissions": [
    "topSites"
  ],
  "browser_action": {
    "default_icon": {
      "19": "images/Icon-19.png",
      "38": "images/Icon-38.png"
    },
    "default_title": "Topsites",
    "default_popup": "html/topsite.html"
  }
}