message: Prevent removal of constant inputs to passthrough ops.
diff: @@ -85,9 +85,11 @@ bool RemoveTrivialPassthroughOp(GraphTransformation* transformation,
  "Removing %s, keeping its non-constant input array %s and removing %s",
  LogName(*passthru_op), main_input_name, output_name);
  RerouteEdges(output_name, main_input_name, model);
  - } else if (IsDiscardableArray(*model, main_input_name)) {
  + } else if (IsDiscardableArray(*model, main_input_name) &&
  + !IsConstantParameterArray(*model, main_input_name)) {
  transformation->AddMessageF(
  - "Removing %s, keeping its output array %s and removing input %s",
  + "Removing %s, keeping its output array %s and removing non-constant "
  + "input %s",
  LogName(*passthru_op), output_name, main_input_name);
  RerouteEdges(main_input_name, output_name, model);
  } else {
  