message: Use Sampler to record warm up latency distribution (by status).
diff: @@ -52,8 +52,8 @@ auto* load_latency_by_stage = monitoring::Sampler<2>::New(
  "model_path",
  "stage",
  },
  - // Scale of 10, power of 1.5 with bucket count 36 (~20 minutes).
  - monitoring::Buckets::Exponential(10, 1.5, 36));
  + // Scale of 10, power of 1.8 with bucket count 33 (~20 minutes).
  + monitoring::Buckets::Exponential(10, 1.8, 33));
  constexpr char kLoadAttemptFail[] = "fail";
  constexpr char kLoadAttemptSuccess[] = "success";
  