message: Remove unused proto imports.
diff: syntax = "proto3";
  -option cc_enable_arenas = true;
  package tensorflow;
  -import "tensorflow/core/framework/graph.proto";
  -import "tensorflow/core/protobuf/cluster.proto";
  import "tensorflow/core/protobuf/master.proto";
  +option cc_enable_arenas = true;
  +
  // Records the creation of a new replay session. We record the device listing
  // here to capture the state of the cluster.
  message NewReplaySession {
  