Revert of 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 51b02c2d214aface2edf18c53c79562bd82f0692..b7e5459df0dc6511945c6df3e3b34ac25cb0a8b8 100644
--- a/media/filters/ffmpeg_audio_decoder.cc
+++ b/media/filters/ffmpeg_audio_decoder.cc
@@ -249,6 +249,16 @@
     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);