chromium/extensions/test/data/extension_icon_manager/manifest.json

{
  "name": "An extension with multiple icon sizes",
  "version": "1",
  "manifest_version": 3,
  "icons": {
    "16": "16.png",
    "24": "24.png",
    "32": "32.png"
    // Adding more icons here? Please ensure that we do not have
    // a 48 x 48 icon (300% scale) here as that would mean losing
    // test coverage in ExtensionIconManagerTest.ScaleFactors.
  }
}