Need API in QtWebEngine for calling blink::WebSecurityPolicy::addOriginAccessWhitelistEntry

I'm trying to implement support for "about:konqueror" using

page()->setContent(htmlData, "text/html", "about:konqueror")

where the html data loads icons and css stylesheets from file:/// URLs. This however leads to the following error:

Not allowed to load local resource: file:///usr/share/icons/breeze/places/32/user-home.svg

I tried many things to get around this. The only thing that I found to work was to switch to a different scheme than "about" (I tried "konq") and to add this line:

blink::WebSecurityPolicy::addOriginAccessWhitelistEntry(blink::WebURL(GURL("konq:")), "file", "", true);

to ContentRendererClientQt::RenderThreadStarted.
It doesn't work with "about:" because shouldTreatAsUniqueOrigin() returns true for "about:", because shouldTreatURLSchemeAsNoAccess() returns true for { "about", "javascript", "data" },
and addOriginAccessWhitelistEntry asserts that the origin is NOT "unique", i.e. it cannot be done for one of these schemes.

It seems to me that the support for Chrome's about: went down a bit too much into blink, but whatever. I can switch to another scheme, I guess.

Can there be an API in QtWebEngine for registering schemes that should be allowed to load local files?
(I'm going to need this for many more schemes than the "about" replacement... "man:/ls" also generates HTML which needs to load local files, etc.)