Examine source code of tabGrouper

{
  "manifest_version": 2,
  "name": "tabGrouper",
  "version": "1.1",
  "description": "Groups tabs together with the same domain",
  "icons": {
    "48": "icons/grouper.png"
  },
  "browser_action": {
    "default_icon": "icons/grouper.png",
    "default_title": "tabGrouper"
  },
  "background": {
    "scripts": [
      "grouper.js"
    ]
  },
  "permissions": [
    "<all_urls>",
    "tabs",
    "webRequest"
  ],
  "commands": {
    "toggle-feature": {
      "suggested_key": {
        "default": "Ctrl+Shift+Y"
      },
      "description": "send a grouping event"
    }
  }
}