Add chrome-safebrowsing people to download_stats.cc OWNERS

Bug: 863968
Change-Id: If488c9b2e6f73451d9e72b623be9148dc75ffb29
Reviewed-on: https://chromium-review.googlesource.com/1138639Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Nathan Parker <nparker@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575333}

components/download/internal/common/OWNERS

+# For adding new file types
+per-file download_stats.cc=file://chrome/browser/resources/safe_browsing/OWNERS