Examine source code of Devil Debugger

{
  "manifest_version" : 2 ,
  "name" : "Devil Debugger",
  "version" : "2.0.0",
  "author": "Vignesh Miller",
  "description" : "A hell-precise visual debugger for the web. Outline every element by tag, nesting depth or mono color, and inspect any node live — tag, id, classes and box size — without leaving the page.",
  "permissions" : [
    "tabs" ,
    "storage" ,
    "<all_urls>" 
  ],
  "browser_action" : {
    "default_popup" : "popup.html",
    "default_title" : "Devil Debugger — toggle visual debugging",
    "default_icon" : {
      "128" : "icons/128.png"
    }
  },
  "icons" : {
    "128" : "icons/128.png"
  },
  "background" : {
    "scripts" : [
      "background.js" 
    ],
    "persistent" : false 
  },
  "content_scripts" : [
    {
      "matches" : [
        "<all_urls>" 
      ],
      "js" : [
        "shared-data.js" ,
        "content.js" 
      ],
      "run_at" : "document_idle" ,
      "all_frames" : false 
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "starvicki2002@gmail.com",
      "strict_min_version": "91.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}