Examine source code of Simple Screen Capture

{
  "manifest_version": 2,
  "name": "Simple Screen Capture",
  "version": "1.0",
  "description": "Capture the currently visible part of the webpage.",
  "icons": {
    "48": "icons/icon-48.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/icon-48.png",
    "default_title": "Capture Screen"
  },
  "permissions": [
    "<all_urls>",
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{634b3ef7-3359-4c43-a3d2-dac144cc3a8e}"
    }
  }
}