Fix incorrect opus seek preroll and flaky pre-skip removal.

media/filters/opus_audio_decoder.h

Index: media/filters/opus_audio_decoder.h
diff --git a/media/filters/opus_audio_decoder.h b/media/filters/opus_audio_decoder.h
index 3b0cd7164ae6d3e054a632be2a6a82264c50f6cf..0937b81ae10059b7954b46dbcc2f152eb66f351b 100644
--- a/media/filters/opus_audio_decoder.h
+++ b/media/filters/opus_audio_decoder.h
@@ -57,9 +57,10 @@ class MEDIA_EXPORT OpusAudioDecoder : public AudioDecoder {
   OutputCB output_cb_;
   OpusMSDecoder* opus_decoder_;
 
-  // When the input timestamp is |start_input_timestamp_| the decoder needs to
-  // drop |config_.codec_delay()| frames.
-  base::TimeDelta start_input_timestamp_;
+  // Hack to allow MSE to correctly support webm codec delay for opus; if an
+  // input buffer comes in with a timestamp less than this and no discard
+  // padding, the buffer will be marked for discard up to |start_timestamp_|.
+  base::TimeDelta start_timestamp_;
 
   scoped_ptr<AudioDiscardHelper> discard_helper_;