Examine source code of Gmail Unread Counter

{
  "manifest_version": 2,
  "name": "Gmail Unread Counter",
  "version": "1.0.1",
  "description": "Displays the number of unread Gmail messages on the toolbar icon with real-time polling.",
  "permissions": [
    "alarms",
    "storage",
    "notifications",
    "https://mail.google.com/*"
  ],
  "browser_action": {
    "default_icon": {
      "16": "icons/gmail-16.png",
      "32": "icons/gmail-32.png",
      "48": "icons/gmail-48.png"
    },
    "default_popup": "popup.html",
    "default_title": "Gmail Unread Counter"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "icons": {
    "48": "icons/gmail-48.png",
    "128": "icons/gmail-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "gmail-unread-counter@forrestgrump",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    },
    "gecko_android": {
      "strict_min_version": "142.0"
    }
  }
}