Allow custom audio processing by exposing AudioProcessingModule (webrtc-sdk#85)

* apm

* progress

* expose raw buffer

* config

* runtime delegate update

* always create audio processing adapter

* delegate nullable

* dynamic delegate update thread safety

* fix delegate life cycle when swapped

* refactor

* avoid crash when no apm is passed in

* format

* make delegate weak & docs

* fix memory issue

Author: hiroshihorie

sdk/objc/api/peerconnection/RTCAudioTrack.mm

@@ -212,6 +212,7 @@ - (instancetype)initWithFactory:(RTC_OBJC_TYPE(RTCPeerConnectionFactory) *)facto
   NSParameterAssert(type == RTCMediaStreamTrackTypeAudio);
   if (self = [super initWithFactory:factory nativeTrack:nativeTrack type:type]) {
     RTC_LOG(LS_INFO) << "RTCAudioTrack init";
+    _lock = OS_UNFAIR_LOCK_INIT;
     _renderers = [NSHashTable weakObjectsHashTable];
     _audioConverter = new rtc::RefCountedObject<webrtc::AudioSinkConverter>(self, &_lock);
   }

sdk/objc/api/peerconnection/RTCPeerConnectionFactory+Native.h

@@ -73,12 +73,6 @@ NS_ASSUME_NONNULL_BEGIN
     initWithEncoderFactory:(nullable id<RTC_OBJC_TYPE(RTCVideoEncoderFactory)>)encoderFactory
             decoderFactory:(nullable id<RTC_OBJC_TYPE(RTCVideoDecoderFactory)>)decoderFactory;
 
-- (instancetype)
-    initWithBypassVoiceProcessing:(BOOL)bypassVoiceProcessing
-                   encoderFactory:(nullable id<RTC_OBJC_TYPE(RTCVideoEncoderFactory)>)encoderFactory
-                   decoderFactory:
-                       (nullable id<RTC_OBJC_TYPE(RTCVideoDecoderFactory)>)decoderFactory;
-
 /** Initialize an RTCPeerConnection with a configuration, constraints, and
  *  dependencies.
  */