Revert of H264POC: Allow gaps in frame_num.

media/gpu/vt_video_decode_accelerator_mac.cc

Index: media/gpu/vt_video_decode_accelerator_mac.cc
diff --git a/media/gpu/vt_video_decode_accelerator_mac.cc b/media/gpu/vt_video_decode_accelerator_mac.cc
index ebbb7835da9d8f19fff3b637269e00e5debb3374..2f989e30077381c23f569d50e8873196e0b2a700 100644
--- a/media/gpu/vt_video_decode_accelerator_mac.cc
+++ b/media/gpu/vt_video_decode_accelerator_mac.cc
@@ -750,8 +750,8 @@
   // Send the frame for decoding.
   // Asynchronous Decompression allows for parallel submission of frames
   // (without it, DecodeFrame() does not return until the frame has been
-  // decoded). We don't enable Temporal Processing because we are not passing
-  // timestamps anyway.
+  // decoded). We don't enable Temporal Processing so that frames are always
+  // returned in decode order; this makes it easier to avoid deadlock.
   VTDecodeFrameFlags decode_flags =
       kVTDecodeFrame_EnableAsynchronousDecompression;
   status = VTDecompressionSessionDecodeFrame(