Examine source code of AlienAlien

{
  "manifest_version": 2,
  "name": "AlienAlien",
  "version": "1.2",
  "description": "Adds UFOs to the browser",
  "icons": {
    "48": "icons/alienalien-48.png"
  },
  "browser_action": {
    "browser_style": true,
    "default_popup": "popup/popup.html",
    "default_icon": {
      "48": "icons/alienalien-48.png"
    }
  },
  "web_accessible_resources": [
    "images/alien.gif"
  ],
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ]
}