Examine source code of In-Line Calculator

{
  "name": "In-Line Calculator",
  "version": "1.5.0",
  "manifest_version": 2,
  "description": "Evaluate simple mathematical expressions as you type!",
  "permissions": [
    "storage"
  ],
  "icons": {
    "16": "img/thumb_16.png",
    "48": "img/thumb_48.png",
    "128": "img/thumb_128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "js/content.js"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "in-line_calculator@charlie-volow.com"
    }
  }
}