This requires modifying Tools/Scripts/webkitpy/layout_tests/port/base.py to recognize virtual/mojo-loading/external/wpt as wptserve tests. Probably a simple change to is_wptserve_test() does the trick.

But this has some cost:
- TestExpectations need to be duplicated for virtual/mojo-loading
- Test runtime will increase as SW tests are basically run twice.

Currently most tests in WPT and SW are duplicated so there's no strong need now. But as tests get migrated we can more strongly consider doing this.