message: Let toco handle Placeholders in full flex mode.
diff: @@ -2113,6 +2113,14 @@ using ConverterType = tensorflow::Status (*)(
  Model* model);
  using ConverterMapType = std::unordered_map<std::string, ConverterType>;
  +ConverterMapType GetTensorFlowNodeConverterMapForFlex() {
  + return std::unordered_map<std::string, ConverterType>({
  + // We need to let TCO convert Placeholder information into
  + // array data, so that the data types are correct.
  + {"Placeholder", ConvertPlaceholderOperator},
  + });
  +}
  +
  ConverterMapType GetTensorFlowNodeConverterMap() {
  return std::unordered_map<std::string, ConverterType>({
  {"Add", ConvertSimpleOperator<AddOperator, 2>},
  @@ -2269,6 +2277,8 @@ std::unique_ptr<Model> ImportTensorFlowGraphDef(
  // converted to TFLite Flex ops.
  if (!tf_import_flags.import_all_ops_as_unsupported) {
  converter_map = internal::GetTensorFlowNodeConverterMap();
  + } else {
  + converter_map = internal::GetTensorFlowNodeConverterMapForFlex();
  }
  for (auto node : inlined_graph.node()) {
  