Examine source code of Resource Weight Meter

{
  "manifest_version": 2,
  "name": "Resource Weight Meter",
  "version": "1.6",
  "description": "Profile a page's download footprint at a glance. It groups every loaded resource by category — JavaScript, styles, images, fonts, media, requests — and shows how many bytes and files each one adds up to.",
  "icons": {
    "32": "graphics/icon-32.png",
    "48": "graphics/icon-48.png",
    "64": "graphics/icon-64.png",
    "96": "graphics/icon-96.png",
    "128": "graphics/icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c15812cc-532f-4873-99d9-fdf661e0d07a}",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_title": "Resource Weight Meter",
    "default_popup": "app/popup.html",
    "default_icon": {
      "32": "graphics/icon-32.png",
      "48": "graphics/icon-48.png",
      "64": "graphics/icon-64.png"
    }
  }
}