Reland of Make RtcEventLogImpl to use a TaskQueue instead of a helper-thread

webrtc/pc/peerconnectionfactory.cc

Index: webrtc/pc/peerconnectionfactory.cc
diff --git a/webrtc/pc/peerconnectionfactory.cc b/webrtc/pc/peerconnectionfactory.cc
index d4ee405f1a3e55d0c9d6205510b4e831e94c9cea..6da4669773dc597f77be92c1a5a07c626ae3066d 100644
--- a/webrtc/pc/peerconnectionfactory.cc
+++ b/webrtc/pc/peerconnectionfactory.cc
@@ -262,8 +262,9 @@ PeerConnectionFactory::CreatePeerConnection(
                                allocator.get(), options_.network_ignore_mask));
 
   std::unique_ptr<RtcEventLog> event_log =
-      event_log_factory_ ? event_log_factory_->CreateRtcEventLog()
-                         : rtc::MakeUnique<RtcEventLogNullImpl>();
+      worker_thread_->Invoke<std::unique_ptr<RtcEventLog>>(
+          RTC_FROM_HERE,
+          rtc::Bind(&PeerConnectionFactory::CreateRtcEventLog_w, this));
 
   std::unique_ptr<Call> call = worker_thread_->Invoke<std::unique_ptr<Call>>(
       RTC_FROM_HERE,
@@ -331,6 +332,11 @@ rtc::Thread* PeerConnectionFactory::network_thread() {
   return network_thread_;
 }
 
+std::unique_ptr<RtcEventLog> PeerConnectionFactory::CreateRtcEventLog_w() {
+  return event_log_factory_ ? event_log_factory_->CreateRtcEventLog()
+                            : rtc::MakeUnique<RtcEventLogNullImpl>();
+}
+
 std::unique_ptr<Call> PeerConnectionFactory::CreateCall_w(
     RtcEventLog* event_log) {
   const int kMinBandwidthBps = 30000;