Examine source code of Analog Percent Clock

{
  "name": "Analog Percent Clock",
  "version": "1.2resigned1",
  "description": "Single-hand clock showing percentage of today that's already gone",
  "manifest_version": 2,
  "icons": {
    "128": "icon.png"
  },
  "chrome_url_overrides": {
    "newtab": "clock.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f9e6079c-35cc-4420-b617-ae933b99494f}"
    }
  }
}