Examine source code of Tab 4loser

{
  "manifest_version": 2,
  "name": "Tab Closer",
  "version": "1.0",
  "description": "Closes all other tabs except the one you're using.",
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Close Other Tabs",
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "tabcloser-unique-57921@addon.com"
    }
  }
}