electron/shell/common/extensions/api/_api_features.json

{
  "tabs": {
    "channel": "stable",
    "extension_types": ["extension"],
    "contexts": ["blessed_extension"]
  },
  "extension": {
    "channel": "stable",
    "extension_types": ["extension"],
    "contexts": ["blessed_extension"]
  },
  "extension.getURL": {
    "contexts": ["blessed_extension", "unblessed_extension", "content_script"]
  }
}