video_replay: wrap main thread

Fix for the DCHECK described in
  from https://bugs.chromium.org/p/webrtc/issues/detail?id=11800#c3

BUG=None

Change-Id: I18e6e12431c1d1c033f5e219156afde00b9ae1e9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/180420
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
Cr-Commit-Position: refs/heads/master@{#31908}

rtc_tools/video_replay.cc

@@ -521,6 +521,7 @@ int main(int argc, char* argv[]) {
       absl::GetFlag(FLAGS_transmission_offset_id)));
   RTC_CHECK(ValidateInputFilenameNotEmpty(absl::GetFlag(FLAGS_input_file)));
 
+  rtc::ThreadManager::Instance()->WrapCurrentThread();
   webrtc::test::RunTest(webrtc::RtpReplay);
   return 0;
 }