message: Fix liveness performance regression
  Summary: Fix pass-by-value typos
  Test Plan: CI
  Reviewers: #tensorflow, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved, jackh
  Subscribers: jackh
  Maniphest Tasks: T66489
diff: @@ -116,7 +116,7 @@ bool IsFinalResult(const HloInstruction* inst) {
  void UpdateLivenessBackwards(
  const HloInstruction* inst, const HloPoplarBuffer* buffer,
  - const absl::flat_hash_map<const HloPoplarBuffer*, const HloInstruction*>
  + const absl::flat_hash_map<const HloPoplarBuffer*, const HloInstruction*>&
  buffer_creators,
  HloPoplarBufferIdSet& live_set) {
  // Since we're going backwards we kill a buffer when it's defined. The only
  @@ -231,7 +231,7 @@ int64_t MemoryUsageOfBufferSet(
  }
  int64_t MemoryUsageOfComputations(
  - const std::vector<HloComputation*> computations,
  + const std::vector<HloComputation*>& computations,
  const absl::flat_hash_map<const HloComputation*, int64_t>&
  computation_costs_in_bytes) {
  const int64_t memory_usage = absl::c_accumulate(
  