message: Fix `base64_fuzz` as it currently breaks on OSSFuzz.
  Also simplifies code a little by removing a few not-needed casts.
diff: @@ -25,20 +25,15 @@ limitations under the License.
  namespace {
  extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
  - uint8_t *byte_data = const_cast<uint8_t *>(data);
  - char *char_data = reinterpret_cast<char *>(byte_data);
  -
  - tensorflow::StringPiece original_sp =
  - tensorflow::StringPiece(char_data, size);
  -
  - string encoded_string;
  - string decoded_string;
  + std::string input(reinterpret_cast<const char *>(data));
  + std::string encoded_string;
  + std::string decoded_string;
  tensorflow::Status s;
  - s = tensorflow::Base64Encode(original_sp, &encoded_string);
  + s = tensorflow::Base64Encode(input, &encoded_string);
  assert(s.ok());
  s = tensorflow::Base64Decode(encoded_string, &decoded_string);
  assert(s.ok());
  - assert(original_sp == decoded_string);
  + assert(input == decoded_string);
  return 0;
  }
  