Examine source code of Invert Tab Selection

{
  "author": "igorlogius",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_area": "tabstrip"
  },
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Ctrl+Alt+I"
      }
    }
  },
  "description": "Invert the current tab selection",
  "icons": {
    "128": "icon.png"
  },
  "manifest_version": 2,
  "name": "Invert Tab Selection",
  "permissions": [
    "tabs",
    "menus"
  ],
  "version": "1.1.3",
  "browser_specific_settings": {
    "gecko": {
      "id": "{6d0cbbb0-1e0f-420a-9aa3-b344c5592e1c}"
    }
  }
}