Make the output_period_ms argument to StartRtcEventLog optional

Intended to ease transition to new log format.

Bug: webrtc:6463, webrtc:8111
Change-Id: Icadaedb6a6a7d31038a45ff5eb0b054528f00f2f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/135944
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27920}

api/peer_connection_interface.cc

@@ -182,6 +182,11 @@ bool PeerConnectionInterface::StartRtcEventLog(
   return false;
 }
 
+bool PeerConnectionInterface::StartRtcEventLog(
+    std::unique_ptr<RtcEventLogOutput> output) {
+  return false;
+}
+
 rtc::scoped_refptr<DtlsTransportInterface>
 PeerConnectionInterface::LookupDtlsTransportByMid(const std::string& mid) {
   RTC_NOTREACHED();

api/peer_connection_interface.h

@@ -1074,8 +1074,14 @@ class RTC_EXPORT PeerConnectionInterface : public rtc::RefCountInterface {
   // |output| and passes it on to Call, which will take the ownership. If the
   // operation fails the output will be closed and deallocated. The event log
   // will send serialized events to the output object every |output_period_ms|.
+  // Applications using the event log should generally make their own trade-off
+  // regarding the output period. A long period is generally more efficient,
+  // with potential drawbacks being more bursty thread usage, and more events
+  // lost in case the application crashes. If the |output_period_ms| argument is
+  // omitted, webrtc selects a default deemed to be workable in most cases.
   virtual bool StartRtcEventLog(std::unique_ptr<RtcEventLogOutput> output,
                                 int64_t output_period_ms);
+  virtual bool StartRtcEventLog(std::unique_ptr<RtcEventLogOutput> output);
 
   // Stops logging the RtcEventLog.
   // TODO(ivoc): Make this pure virtual when Chrome is updated.

pc/peer_connection.cc

@@ -3791,6 +3791,12 @@ bool PeerConnection::StartRtcEventLog(std::unique_ptr<RtcEventLogOutput> output,
       RTC_FROM_HERE, Functor{this, std::move(output), output_period_ms});
 }
 
+bool PeerConnection::StartRtcEventLog(
+    std::unique_ptr<RtcEventLogOutput> output) {
+  return StartRtcEventLog(std::move(output),
+                          webrtc::RtcEventLog::kImmediateOutput);
+}
+
 void PeerConnection::StopRtcEventLog() {
   worker_thread()->Invoke<void>(
       RTC_FROM_HERE, rtc::Bind(&PeerConnection::StopRtcEventLog_w, this));

pc/peer_connection.h

@@ -211,6 +211,7 @@ class PeerConnection : public PeerConnectionInternal,
                                        int64_t max_size_bytes) override;
   bool StartRtcEventLog(std::unique_ptr<RtcEventLogOutput> output,
                         int64_t output_period_ms) override;
+  bool StartRtcEventLog(std::unique_ptr<RtcEventLogOutput> output) override;
   void StopRtcEventLog() override;
 
   void Close() override;