Currently, it's possible to select read-only UserAgent properties and remove them.
<rdar://problem/47016335>
Created attachment 358240 [details] Patch
Comment on attachment 358240 [details] Patch rs=me
Comment on attachment 358240 [details] Patch Clearing flags on attachment: 358240 Committed r239585: <https://trac.webkit.org/changeset/239585>
All reviewed patches have been landed. Closing bug.