message: Parse offload_gradient_accumulation_buffers in backend config
  Test Plan: Hardware test `pytest -s -v --forked test_batch_serial_pipelining.py` still passes.
  Reviewers: georgep, #tensorflow, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved
  Maniphest Tasks: T27846
diff: @@ -124,6 +124,17 @@ StatusOr<bool> ParsePoplarBackendConfig::Run(HloModule* module) {
  TF_ASSIGN_OR_RETURN(auto offload_variables,
  ParseThreeState(offload_variables_str));
  pipeline_config->set_offload_variables(offload_variables);
  +
  + // Set the offload gradient accumulation buffers flag.
  + TF_ASSIGN_OR_RETURN(
  + std::string offload_gradient_accumulation_buffers_str,
  + GetAttribute(attributes,
  + OFFLOAD_GRADIENT_ACCUMULATION_BUFFERS));
  + TF_ASSIGN_OR_RETURN(
  + auto offload_gradient_accumulation_buffers,
  + ParseThreeState(offload_gradient_accumulation_buffers_str));
  + pipeline_config->set_offload_gradient_accumulation_buffers(
  + offload_gradient_accumulation_buffers);
  break;
  }
  case PoplarBackendConfig::CallConfig::PipelineStage:
  