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..49e357a1c979cc7be9cdf7a09ca8c13bc9ad42df 100644
--- a/webrtc/pc/peerconnectionfactory.cc
+++ b/webrtc/pc/peerconnectionfactory.cc
@@ -21,7 +21,6 @@
 #include "webrtc/logging/rtc_event_log/rtc_event_log.h"
 #include "webrtc/rtc_base/bind.h"
 #include "webrtc/rtc_base/checks.h"
-#include "webrtc/rtc_base/ptr_util.h"
 // Adding 'nogncheck' to disable the gn include headers check to support modular
 // WebRTC build targets.
 // TODO(zhihuang): This wouldn't be necessary if the interface and
@@ -262,8 +261,9 @@ PeerConnectionFactory::CreatePeerConnection(
                                allocator.get(), options_.network_ignore_mask));
 
   std::unique_ptr<RtcEventLog> event_log =

[eladalon, 2017/09/05 13:04:32]

There's a trade-off between Invoke()-ing twice (blocking function), which makes
for cleaner code, and doing two different things in (a renamed version of)
CreateCall_w, which is more efficient. Thoughts?

-      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 +331,11 @@ 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;