Examine source code of Resize Window To Element

{
  "manifest_version": 2,
  "name": "Resize Window To Element",
  "version": "1.2.1",
  "description": "Resizes the Firefox window to the size of an element.",
  "permissions": [
    "contextMenus",
    "activeTab",
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ]
    }
  ],
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "browser_action": {
    "default_icon": {
      "16": "icon16.png",
      "32": "icon32.png",
      "48": "icon.png"
    },
    "default_title": "Start Element Picker"
  },
  "icons": {
    "16": "icon16.png",
    "32": "icon32.png",
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c935f771-f7d4-42b0-bd84-9359d3a0df70}"
    }
  }
}