GitLab

- adds more native_value_traits_impl.h includes
- adds include for a union type


Bug: 839389
Change-Id: I454f2e5a2e9d757439ee3def1edafa53c18bb860
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2060443Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Hitoshi Yoshida <peria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742538}