I actually hit this in unified builds after making small, unrelated changes, but presumably it also breaks non-unified builds. SessionStorage.h is missing a couple of includes.
Created attachment 447000 [details] Patch
Comment on attachment 447000 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=447000&action=review > Source/WebKit/NetworkProcess/storage/SessionStorageManager.h:31 > +#include <WebCore/ClientOrigin.h> Should likely be a forward declaration.
Created attachment 447015 [details] Patch
This was fixed by unreviewed change https://trac.webkit.org/changeset/286946/webkit