Examine source code of Background Sound

{
  "manifest_version": 2,
  "name": "Background Sound",
  "version": "1.0",
  "description": "Play background music or nature sounds while working.",
  "icons": {
    "48": "icons/icon.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/icon.png",
    "default_title": "Background Sound",
    "default_popup": "popup.html"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{a2e720b3-ab52-45a0-9e8f-012267d37b46}"
    }
  }
}