One WebRTC APM instance is enough

Stop using APM in the Blink peer connection module, since the active
APM instance is owned and handled in the Blink media stream module.
Less CPU usage at call initialization, less memory and more importantly
no misleading logs from APM (in particular, those from
`AudioProcessing::ApplyConfig()`).

Tested: chromium compiled, appr.tc call successfully made, logs now
look ok.

Bug: 1136418
Change-Id: I83fd5c2c04da279e997bef76cdd18872463f5b4d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2461107Reviewed-by: Tommi <tommi@chromium.org>
Commit-Queue: Ale Bzk <alessiob@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815115}

third_party/blink/renderer/modules/peerconnection/peer_connection_dependency_factory.cc

@@ -55,7 +55,6 @@
 #include "third_party/webrtc/media/engine/fake_video_codec_factory.h"
 #include "third_party/webrtc/media/engine/multiplex_codec_factory.h"
 #include "third_party/webrtc/media/engine/webrtc_media_engine.h"
-#include "third_party/webrtc/modules/audio_processing/include/audio_processing.h"
 #include "third_party/webrtc/modules/video_coding/codecs/h264/include/h264.h"
 #include "third_party/webrtc/rtc_base/openssl_stream_adapter.h"
 #include "third_party/webrtc/rtc_base/ref_counted_object.h"
@@ -323,7 +322,9 @@ void PeerConnectionDependencyFactory::InitializeSignalingThread(
   media_deps.audio_decoder_factory = blink::CreateWebrtcAudioDecoderFactory();
   media_deps.video_encoder_factory = std::move(webrtc_encoder_factory);
   media_deps.video_decoder_factory = std::move(webrtc_decoder_factory);
-  media_deps.audio_processing = webrtc::AudioProcessingBuilder().Create();
+  // Audio Processing Module (APM) instances are owned and handled by the Blink
+  // media stream module.
+  DCHECK_EQ(media_deps.audio_processing, nullptr);
   pcf_deps.media_engine = cricket::CreateMediaEngine(std::move(media_deps));
   pc_factory_ = webrtc::CreateModularPeerConnectionFactory(std::move(pcf_deps));
   CHECK(pc_factory_.get());