When building All with gyp for iOS, we build some targets that are not build with gn. Investigate whether we want to build them with gn, and if so, port them.

List of targets build with gyp and not build with gn:
  accessibility_unittests
  crnet_consumer
  crnet_dummy
  crnet_test
  display_unittests
  dump_cache
  mojo_common_unittests
  mojo_public_bindings_unittests
  mojo_public_system_unittests
  mojo_system_unittests
  snapshot_unittests