[automerger skipped] Update stats_log.proto for cts backfill am: 40bb3febea -s ours am: 6a44800b36 -s ours

am skip reason: Merged-In I57ea08b6d3d54e4d10034bcc52fd3340033ef887 with SHA-1 9363f5e0bd is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/modules/StatsD/+/15623716

Change-Id: Ife0fee5f341ec6beeb1e8769f9869f16c17abe38