VideoRtpReceiver & AudioRtpReceiver threading fixes.

For implementations where the signaling and worker threads are not
the same thread, this significantly cuts down on Thread::Invoke()s that
would block the signaling thread while waiting for the worker thread.

For Audio and Video Rtp receivers, the following methods now do not
block the signaling thread:
* GetParameters
* SetJitterBufferMinimumDelay
* GetSources
* SetFrameDecryptor / GetFrameDecryptor
* SetDepacketizerToDecoderFrameTransformer

Importantly this change also makes the track() accessor accessible
directly from the application thread (bypassing the proxy) since
for receiver objects, the track object is const.

Other changes:

* Remove RefCountedObject inheritance, use make_ref_counted instead.
* Every member variable in the rtp receiver classes is now RTC_GUARDED
* Stop() now fully clears up worker thread state, and Stop() is
  consistently called before destruction. This means that there's one
  thread hop instead of at least 4 before (sometimes more), per receiver.
* OnChanged triggered volume for audio tracks is done asynchronously.
* Deleted most of the JitterBufferDelay implementation. Turns out that
  it was largely unnecessary overhead and complexity.

It seems that these two classes are copy/pasted to a large extent
so further refactoring would be good in the future, as to not have to
fix each issue twice.

Bug: chromium:1184611
Change-Id: I1ba5c3abbd1b0571f7d12850d64004fd2d83e5e2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/218605
Commit-Queue: Tommi <tommi@webrtc.org>
Reviewed-by: Markus Handell <handellm@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34022}
diff --git a/api/rtp_receiver_interface.h b/api/rtp_receiver_interface.h
index e0ace54..d2645ed 100644
--- a/api/rtp_receiver_interface.h
+++ b/api/rtp_receiver_interface.h
@@ -100,11 +100,13 @@
   // before it is sent across the network. This will decrypt the entire frame
   // using the user provided decryption mechanism regardless of whether SRTP is
   // enabled or not.
+  // TODO(bugs.webrtc.org/12772): Remove.
   virtual void SetFrameDecryptor(
       rtc::scoped_refptr<FrameDecryptorInterface> frame_decryptor);
 
   // Returns a pointer to the frame decryptor set previously by the
   // user. This can be used to update the state of the object.
+  // TODO(bugs.webrtc.org/12772): Remove.
   virtual rtc::scoped_refptr<FrameDecryptorInterface> GetFrameDecryptor() const;
 
   // Sets a frame transformer between the depacketizer and the decoder to enable
@@ -120,27 +122,31 @@
 // Define proxy for RtpReceiverInterface.
 // TODO(deadbeef): Move this to .cc file and out of api/. What threads methods
 // are called on is an implementation detail.
-BEGIN_PRIMARY_PROXY_MAP(RtpReceiver)
+BEGIN_PROXY_MAP(RtpReceiver)
 PROXY_PRIMARY_THREAD_DESTRUCTOR()
-PROXY_CONSTMETHOD0(rtc::scoped_refptr<MediaStreamTrackInterface>, track)
+BYPASS_PROXY_CONSTMETHOD0(rtc::scoped_refptr<MediaStreamTrackInterface>, track)
 PROXY_CONSTMETHOD0(rtc::scoped_refptr<DtlsTransportInterface>, dtls_transport)
 PROXY_CONSTMETHOD0(std::vector<std::string>, stream_ids)
 PROXY_CONSTMETHOD0(std::vector<rtc::scoped_refptr<MediaStreamInterface>>,
                    streams)
 BYPASS_PROXY_CONSTMETHOD0(cricket::MediaType, media_type)
 BYPASS_PROXY_CONSTMETHOD0(std::string, id)
-PROXY_CONSTMETHOD0(RtpParameters, GetParameters)
+PROXY_SECONDARY_CONSTMETHOD0(RtpParameters, GetParameters)
 PROXY_METHOD1(void, SetObserver, RtpReceiverObserverInterface*)
-PROXY_METHOD1(void, SetJitterBufferMinimumDelay, absl::optional<double>)
-PROXY_CONSTMETHOD0(std::vector<RtpSource>, GetSources)
-PROXY_METHOD1(void,
-              SetFrameDecryptor,
-              rtc::scoped_refptr<FrameDecryptorInterface>)
-PROXY_CONSTMETHOD0(rtc::scoped_refptr<FrameDecryptorInterface>,
-                   GetFrameDecryptor)
-PROXY_METHOD1(void,
-              SetDepacketizerToDecoderFrameTransformer,
-              rtc::scoped_refptr<FrameTransformerInterface>)
+PROXY_SECONDARY_METHOD1(void,
+                        SetJitterBufferMinimumDelay,
+                        absl::optional<double>)
+PROXY_SECONDARY_CONSTMETHOD0(std::vector<RtpSource>, GetSources)
+// TODO(bugs.webrtc.org/12772): Remove.
+PROXY_SECONDARY_METHOD1(void,
+                        SetFrameDecryptor,
+                        rtc::scoped_refptr<FrameDecryptorInterface>)
+// TODO(bugs.webrtc.org/12772): Remove.
+PROXY_SECONDARY_CONSTMETHOD0(rtc::scoped_refptr<FrameDecryptorInterface>,
+                             GetFrameDecryptor)
+PROXY_SECONDARY_METHOD1(void,
+                        SetDepacketizerToDecoderFrameTransformer,
+                        rtc::scoped_refptr<FrameTransformerInterface>)
 END_PROXY_MAP()
 
 }  // namespace webrtc