Fix av sync for webm files with altref video frames. Altref frames...

media/filters/ffmpeg_video_decode_engine.cc

Index: media/filters/ffmpeg_video_decode_engine.cc
===================================================================
--- media/filters/ffmpeg_video_decode_engine.cc	(revision 54794)
+++ media/filters/ffmpeg_video_decode_engine.cc	(working copy)
@@ -133,6 +133,10 @@
   // Let FFmpeg handle presentation timestamp reordering.
   codec_context_->reordered_opaque = buffer->GetTimestamp().InMicroseconds();
 
+  // This is for codecs not using get_buffer to initialize
+  // |av_frame_->reordered_opaque|
+  av_frame_->reordered_opaque = codec_context_->reordered_opaque;
+
   int frame_decoded = 0;
   int result = avcodec_decode_video2(codec_context_,
                                      av_frame_.get(),