In 41850 Mark suggested to fix the problems with wk2 includes through use full include paths and generate forwarding headers for the use case of building wk2 outside of the trunk.
Created attachment 61228 [details]
proof of concept patch
This is just to show how it would look like and to start discussion.
I have created the ResourceRequest.h and two similar in WebKit2/WebProcess because these headers lives in platform specific place inside WebCore.