gensupport directory here (excluding tests, add preserving the original LICENSE) was copied verbatim from google-api-go-client.git, since the original package is in internal now and no longer importable from luci-go.
See [https://crbug.com/1003496] for more info.
This is a temporary solution until luci-go no longer depends on deprecated Cloud Endpoints v1 APIs. Note that copied gensupport still depends on public bits of google-api-go-client.git, so if they drift apart too much, stuff will break.