Examine source code of Focus Follows Mouse

{
  "name": "Focus Follows Mouse",
  "description": "A productivity tool which automatically focuses form elements and links.",
  "version": "1.2resigned1",
  "icons": {
    "64": "focus-follows-mouse-64.png",
    "128": "focus-follows-mouse-128.png"
  },
  "permissions": [
    "tabs",
    "http://*/*",
    "https://*/*"
  ],
  "content_scripts": [
    {
      "matches": [
        "http://*/*",
        "https://*/*"
      ],
      "js": [
        "focus-follows-mouse.js"
      ],
      "run_at": "document_end"
    }
  ],
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "focus-follows-input@spyrosoft.com"
    }
  }
}