message: Avoid unnecessary call to memset().
  The only use of the last_message_ field is in the message() method,
  which converts it to a std::string; that conversion will only look
  at the part up to the first '\0' character.  So it's not necessary
  to null out all the subsequent characters.
diff: @@ -26,7 +26,7 @@ namespace task {
  namespace core {
  int ErrorReporter::Report(const char* format, va_list args) {
  - std::memset(last_message_, 0, kBufferSize);
  + last_message_[0] = '\0';
  int num_characters = vsnprintf(last_message_, kBufferSize, format, args);
  // To mimic tflite::StderrReporter.
  tflite::logging_internal::MinimalLogger::Log(TFLITE_LOG_ERROR, last_message_);
  