PVS-Studio warning V579 for Chromium

std::string TestFileIO::TestParallelReads() {
  ...
  const char* expected_result_1 =
    "__border__abc__border__";
  const char* expected_result_2 =
    "__border__defghijkl__border__";
  if (strncmp(extended_buf_1, expected_result_1,
              sizeof(expected_result_1)) != 0 ||
      strncmp(extended_buf_2, expected_result_2,
              sizeof(expected_result_2)) != 0) {
  ...
}

This suspicious code was found in Chromium project by PVS-Studio static code analyzer.
Warning message is:
V579 The strncmp function receives the pointer and its size as arguments. It is possibly a mistake. Inspect the third argument. ppapi_tests test_file_io.cc 759

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/