GitLab

- Pass -snake-case-generated-files flag if snake_case_source_files
- Apply to_snake_case to pre-defined INCLUDES too.

Bug: 760462
Change-Id: Iacb84b7fb895160cf4791c4570c31d1bd0c62cbc
Reviewed-on: https://chromium-review.googlesource.com/672027Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502960}