Move AudioRendererImpl construction to WebMediaPlayerImpl.

webkit/media/webmediaplayer_impl.cc

Index: webkit/media/webmediaplayer_impl.cc
diff --git a/webkit/media/webmediaplayer_impl.cc b/webkit/media/webmediaplayer_impl.cc
index f5e63331a239b83b285e7a5aa1b881c4b48036b5..9e907e11782aa3cc51cfd7e77a546a28dbf99e3f 100644
--- a/webkit/media/webmediaplayer_impl.cc
+++ b/webkit/media/webmediaplayer_impl.cc
@@ -188,9 +188,12 @@ WebMediaPlayerImpl::WebMediaPlayerImpl(
   filter_collection_->AddVideoRenderer(video_renderer);
   proxy_->set_frame_provider(video_renderer);
 
-  // Create default audio renderer.
+  // Create default audio renderer using the null sink if no sink was provided.
+  if (!audio_renderer_sink) {
+    audio_renderer_sink = new media::NullAudioSink();
+  }
   filter_collection_->AddAudioRenderer(
-      new media::AudioRendererImpl(new media::NullAudioSink()));
+      new media::AudioRendererImpl(audio_renderer_sink));
 
   if (WebKit::WebRuntimeFeatures::isEncryptedMediaEnabled()) {
     decryptor_.reset(new ProxyDecryptor(message_loop_factory_->GetMessageLoop(