Sending invalid frame types and settings as a mechanism to ensure peers ignore them, in conformance with the specification, instead of closing the stream or the connection, has been on our list for a long time.  Now Mike Bishop wrote up a draft proposal, which should be implemented in Chromium.

Proposal:
https://tools.ietf.org/html/draft-bishop-httpbis-grease-00

Announcement:
https://lists.w3.org/Archives/Public/ietf-http-wg/2018AprJun/0221.html

See related document for origin of the backronym "GREASE":
https://tools.ietf.org/html/draft-davidben-tls-grease-01