Examine source code of Brightness Slider Per Tab

{
  "manifest_version": 2,
  "name": "Brightness",
  "version": "1.0.1.4",
  "description": "Adjust brightness per tab",
  "browser_specific_settings": {
    "gecko": {
      "id": "{b9fad55f-f27d-46a6-a257-3ce55a3145a6}"
    }
  },
  "icons": {
    "48": "icons/brightness.svg"
  },
  "permissions": [
    "activeTab",
    "sessions"
  ],
  "browser_action": {
    "default_icon": {
      "48": "icons/brightness.svg"
    },
    "default_title": "Brightness",
    "default_popup": "brightness.html"
  },
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Ctrl+Shift+L"
      }
    }
  }
}