UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:63.0) Gecko/20100101 Firefox/63.0

Steps to reproduce the problem:
1. Send {"id":1, "method":"Target.createBrowserContext"} via DevTools protocol
2. Notice "{'error': {'code': -32000, 'message': 'Not allowed.'}, 'id': 1}" response.

Reproduces on normal & headless. It worked on chrome 69.

What is the expected behavior?

What went wrong?
Target.createBrowserContext returns "Not allowed" error.

Did this work before? Yes Chrome 69

Chrome version: 71.0.3578.80   Channel: stable
OS Version: 10.0
Flash Version: Shockwave Flash 32.0 r0