message: Fix FRAME delimiter is not handled properly in yuv/y4m reader
  Note that sdk/android/api/org/webrtc/FileVideoCapturer.java is handling
  correctly.
  Cr-Commit-Position: refs/heads/main@{#36315}
diff: @@ -204,9 +204,10 @@ rtc::scoped_refptr<Video> OpenY4mFile(const std::string& file_name) {
  const int i420_frame_size = 3 * *width * *height / 2;
  std::vector<fpos_t> frame_positions;
  while (true) {
  - int parse_frame_header_result = -1;
  - if (fscanf(file, "FRAME\n%n", &parse_frame_header_result) != 0 ||
  - parse_frame_header_result == -1) {
  + std::array<char, 6> read_buffer;
  + if (fread(read_buffer.data(), 1, read_buffer.size(), file) <
  + read_buffer.size() ||
  + memcmp(read_buffer.data(), "FRAME\n", read_buffer.size()) != 0) {
  if (!feof(file)) {
  RTC_LOG(LS_ERROR) << "Did not find FRAME header, ignoring rest of file";
  }
  