Ensure DiscardPadding is parsed as a signed integer.

media/filters/opus_audio_decoder.cc

Index: media/filters/opus_audio_decoder.cc
diff --git a/media/filters/opus_audio_decoder.cc b/media/filters/opus_audio_decoder.cc
index e54bf08f502657478d362eb4593eabcb0d2e8aef..479f5887ba9407e891c065cf0731f1766e96152e 100644
--- a/media/filters/opus_audio_decoder.cc
+++ b/media/filters/opus_audio_decoder.cc
@@ -491,12 +491,7 @@ bool OpusAudioDecoder::Decode(const scoped_refptr<DecoderBuffer>& input,
   if (output_timestamp_helper_->base_timestamp() == kNoTimestamp() &&
       !input->end_of_stream()) {
     DCHECK(input->timestamp() != kNoTimestamp());
-    // Adjust the timestamp helper so the base timestamp is corrected for frames
-    // dropped due to codec delay.
     output_timestamp_helper_->SetBaseTimestamp(input->timestamp());
-    output_timestamp_helper_->SetBaseTimestamp(
-        input->timestamp() -
-        output_timestamp_helper_->GetFrameDuration(config_.codec_delay()));
   }
 
   // Trim off any extraneous allocation.
@@ -522,6 +517,8 @@ bool OpusAudioDecoder::Decode(const scoped_refptr<DecoderBuffer>& input,
       }
       output_buffer->get()->TrimEnd(discard_padding);
       frames_to_output -= discard_padding;
+    } else {
+      DCHECK_EQ(input->discard_padding().InMicroseconds(), 0);
     }
   } else {
     frames_to_discard_ -= frames_to_output;