HTMLIFrameElement：featurePolicy 属性
Deprecated
Avoid using this feature in new projects. Feature policy is superseded by permissions policy. This feature may be a candidate for removal from web standards or browsers.
Consider using the following features instead: Permissions policy.
HTMLIFrameElement 接口的 featurePolicy 只读属性返回 FeaturePolicy 接口。该接口提供一个简单的 API，用于检查应用于特定的 iframe 权限策略。