Return 0 instead of AVERROR_EOF for reads at or past the end of a file.

media/filters/ffmpeg_demuxer.cc

Index: media/filters/ffmpeg_demuxer.cc
diff --git a/media/filters/ffmpeg_demuxer.cc b/media/filters/ffmpeg_demuxer.cc
index 17248c6c5ed46eb77ac32815dc8c118636dcc64a..413ff5af6f0287579d2df246486986dcd76bac69 100644
--- a/media/filters/ffmpeg_demuxer.cc
+++ b/media/filters/ffmpeg_demuxer.cc
@@ -336,11 +336,11 @@ int FFmpegDemuxer::Read(int size, uint8* data) {
   if (read_has_failed_)
     return AVERROR_IO;
 
-  // If the read position exceeds the size of the data source. We should return
-  // end-of-file directly.
+  // Even though FFmpeg defines AVERROR_EOF, it's not to be used with I/O
+  // routines.  Instead return 0 for any read at or past EOF.
   int64 file_size;
   if (data_source_->GetSize(&file_size) && read_position_ >= file_size)
-    return AVERROR_EOF;
+    return 0;
 
   // Asynchronous read from data source.
   data_source_->Read(read_position_, size, data,