Examine source code of compact toolbar

{
  "manifest_version": 2,
  "name": "compact-toolbar",
  "version": "1.6.0",
  "description": "You can toggle as hide/show bookmark's titles on bookmark toolbar.",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "background": {
    "scripts": [
      "src/compact-toolbar.js",
      "src/main.js"
    ]
  },
  "applications": {
    "gecko": {
      "id": "compact-toolbar@kakakikikeke.blogspot.com"
    }
  },
  "permissions": [
    "storage",
    "bookmarks"
  ],
  "browser_action": {
    "default_icon": {
      "19": "icons/icon-19-gray.png",
      "38": "icons/icon-38-gray.png"
    }
  },
  "commands": {
    "toggle-compact": {
      "suggested_key": {
        "default": "Ctrl+Shift+Y"
      },
      "description": "Send a 'toggle-compact' event"
    }
  },
  "options_ui": {
    "page": "src/options.html",
    "open_in_tab": false
  }
}