Use ffmpeg for opus decoding, no need to maintain our decoder.

media/test/pipeline_integration_test_base.cc

Index: media/test/pipeline_integration_test_base.cc
diff --git a/media/test/pipeline_integration_test_base.cc b/media/test/pipeline_integration_test_base.cc
index 42b43f3d3347f4fe585be949bf688a537c0f348b..fe89e18de83894853760a1e50df310169869aaa1 100644
--- a/media/test/pipeline_integration_test_base.cc
+++ b/media/test/pipeline_integration_test_base.cc
@@ -23,7 +23,6 @@
 #endif
 #include "media/filters/file_data_source.h"
 #include "media/filters/memory_data_source.h"
-#include "media/filters/opus_audio_decoder.h"
 #include "media/renderers/audio_renderer_impl.h"
 #include "media/renderers/renderer_impl.h"
 #if !defined(MEDIA_DISABLE_LIBVPX)
@@ -344,8 +343,6 @@ std::unique_ptr<Renderer> PipelineIntegrationTestBase::CreateRenderer(
       new FFmpegAudioDecoder(message_loop_.task_runner(), new MediaLog()));
 #endif
 
-  audio_decoders.push_back(new OpusAudioDecoder(message_loop_.task_runner()));
-
   if (!clockless_playback_) {
     audio_sink_ = new NullAudioSink(message_loop_.task_runner());
   } else {