I have run a test with Google developer audit
I got this warning:
Uses deprecated APIs:
Deprecated APIs will eventually be removed from the browser. Learn more.
Deprecation / Warning
Element.createShadowRoot is deprecated and will be removed in M73, around March 2019. Please use Element.attachShadow instead. See https://www.chromestatus.com/features/4507242028072960 for more details.
I am using WordPress 5.1 candidate release. Is GP that is using createShadowRoot?