Fix seeking when the start time is non-zero.

media/filters/ffmpeg_audio_decoder.cc

Index: media/filters/ffmpeg_audio_decoder.cc
diff --git a/media/filters/ffmpeg_audio_decoder.cc b/media/filters/ffmpeg_audio_decoder.cc
index b7e5459df0dc6511945c6df3e3b34ac25cb0a8b8..51b02c2d214aface2edf18c53c79562bd82f0692 100644
--- a/media/filters/ffmpeg_audio_decoder.cc
+++ b/media/filters/ffmpeg_audio_decoder.cc
@@ -249,16 +249,6 @@ void FFmpegAudioDecoder::DecodeBuffer(
     return;
   }
 
-  if (!buffer->end_of_stream() && !discard_helper_->initialized() &&
-      codec_context_->codec_id == AV_CODEC_ID_VORBIS &&
-      buffer->timestamp() < base::TimeDelta()) {
-    // Dropping frames for negative timestamps as outlined in section A.2
-    // in the Vorbis spec. http://xiph.org/vorbis/doc/Vorbis_I_spec.html
-    const int discard_frames =
-        discard_helper_->TimeDeltaToFrames(-buffer->timestamp());
-    discard_helper_->Reset(discard_frames);
-  }
-
   if (!FFmpegDecode(buffer)) {
     state_ = kError;
     decode_cb.Run(kDecodeError);