Rename "metronome" to "decode_metronome".

In preparation for experimentally supporting different types of
metronomes and metronome use cases we'd like to rename for clarity.

This is the first step, which introduces the new name and prefers it if
it is set, but keeps the old name for backwards compat reasons.

Once Chromium has migrated to the new name, we can delete the old name.

Bug: webrtc:15704
Change-Id: I23077bf2415ebb2b2338320c9a14e3bd17d3abb6
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/330020
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Markus Handell <handellm@webrtc.org>
Auto-Submit: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#41319}

api/peer_connection_interface.h

@@ -1441,6 +1441,11 @@ struct RTC_EXPORT PeerConnectionFactoryDependencies final {
   std::unique_ptr<FieldTrialsView> trials;
   std::unique_ptr<RtpTransportControllerSendFactoryInterface>
       transport_controller_send_factory;
+  // Metronome used for decoding, must be called on the worker thread.
+  std::unique_ptr<Metronome> decode_metronome;
+  // Old name for `decode_metronome`.
+  // TODO(https://crbug.com/webrtc/15704): When callers have migrated to
+  // `decode_metronome`, delete this.
   std::unique_ptr<Metronome> metronome;
 
   // Media specific dependencies. Unused when `media_factory == nullptr`.

call/call.cc

@@ -659,11 +659,12 @@ Call::Call(Clock* clock,
       // must be made on `worker_thread_` (i.e. they're one and the same).
       network_thread_(config.network_task_queue_ ? config.network_task_queue_
                                                  : worker_thread_),
-      decode_sync_(config.metronome
-                       ? std::make_unique<DecodeSynchronizer>(clock_,
-                                                              config.metronome,
-                                                              worker_thread_)
-                       : nullptr),
+      decode_sync_(
+          config.decode_metronome
+              ? std::make_unique<DecodeSynchronizer>(clock_,
+                                                     config.decode_metronome,
+                                                     worker_thread_)
+              : nullptr),
       num_cpu_cores_(CpuInfo::DetectNumberOfCores()),
       call_stats_(new CallStats(clock_, worker_thread_)),
       bitrate_allocator_(new BitrateAllocator(this)),

call/call_config.h

@@ -68,7 +68,7 @@ struct CallConfig {
   RtpTransportControllerSendFactoryInterface*
       rtp_transport_controller_send_factory = nullptr;
 
-  Metronome* metronome = nullptr;
+  Metronome* decode_metronome = nullptr;
 
   // Enables send packet batching from the egress RTP sender.
   bool enable_send_packet_batching = false;

pc/peer_connection_factory.cc

@@ -103,7 +103,9 @@ PeerConnectionFactory::PeerConnectionFactory(
           (dependencies->transport_controller_send_factory)
               ? std::move(dependencies->transport_controller_send_factory)
               : std::make_unique<RtpTransportControllerSendFactory>()),
-      metronome_(std::move(dependencies->metronome)) {}
+      decode_metronome_(dependencies->decode_metronome
+                            ? std::move(dependencies->decode_metronome)
+                            : std::move(dependencies->metronome)) {}
 
 PeerConnectionFactory::PeerConnectionFactory(
     PeerConnectionFactoryDependencies dependencies)
@@ -118,7 +120,7 @@ PeerConnectionFactory::~PeerConnectionFactory() {
   RTC_DCHECK_RUN_ON(signaling_thread());
   worker_thread()->BlockingCall([this] {
     RTC_DCHECK_RUN_ON(worker_thread());
-    metronome_ = nullptr;
+    decode_metronome_ = nullptr;
   });
 }
 
@@ -343,7 +345,7 @@ std::unique_ptr<Call> PeerConnectionFactory::CreateCall_w(
 
   call_config.rtp_transport_controller_send_factory =
       transport_controller_send_factory_.get();
-  call_config.metronome = metronome_.get();
+  call_config.decode_metronome = decode_metronome_.get();
   return context_->call_factory()->CreateCall(call_config);
 }
 

pc/peer_connection_factory.h

@@ -147,7 +147,7 @@ class PeerConnectionFactory : public PeerConnectionFactoryInterface {
   std::unique_ptr<NetEqFactory> neteq_factory_;
   const std::unique_ptr<RtpTransportControllerSendFactoryInterface>
       transport_controller_send_factory_;
-  std::unique_ptr<Metronome> metronome_ RTC_GUARDED_BY(worker_thread());
+  std::unique_ptr<Metronome> decode_metronome_ RTC_GUARDED_BY(worker_thread());
 };
 
 }  // namespace webrtc

pc/test/integration_test_helpers.h

@@ -773,7 +773,7 @@ class PeerConnectionIntegrationWrapper : public PeerConnectionObserver,
     pc_factory_dependencies.task_queue_factory =
         CreateDefaultTaskQueueFactory();
     pc_factory_dependencies.trials = std::make_unique<FieldTrialBasedConfig>();
-    pc_factory_dependencies.metronome =
+    pc_factory_dependencies.decode_metronome =
         std::make_unique<TaskQueueMetronome>(TimeDelta::Millis(8));
 
     pc_factory_dependencies.adm = fake_audio_capture_module_;