Examine source code of Dom Element Counter

{
  "manifest_version": 2,
  "name": "Dom Element Counter",
  "version": "1.1resigned1",
  "description": "Display count of DOM elements on page.",
  "icons": {
    "16": "icons/icon-button-16.png",
    "32": "icons/icon-button-32.png",
    "48": "icons/icon-48.png"
  },
  "applications": {
    "gecko": {
      "id": "dom_element_counter@hinst.ru",
      "strict_min_version": "45.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content/content.js"
      ]
    }
  ],
  "browser_action": {
    "browser_style": true,
    "default_icon": "icons/icon-button-32.png",
    "default_title": "Dom Element Counter",
    "default_popup": "popup/page.html"
  },
  "background": {
    "scripts": [
      "background/background.js"
    ]
  }
}