Move RtcEventLog::CreateNull implementation near declaration.

having implementation and declaration in same build target helps
setting dependencies

Bug: None
Change-Id: Ibf22e9c8781def9d84ce4562d0f0eaba5abd39cf
Reviewed-on: https://webrtc-review.googlesource.com/c/106900
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25255}

logging/BUILD.gn

@@ -42,6 +42,7 @@ rtc_source_set("rtc_event_log_api") {
     "../rtc_base:ptr_util",
     "../rtc_base:rtc_base_approved",
     "../rtc_base:rtc_task_queue",
+    "//third_party/abseil-cpp/absl/memory",
   ]
 }
 

logging/rtc_event_log/rtc_event_log.cc

@@ -10,8 +10,14 @@
 
 #include "logging/rtc_event_log/rtc_event_log.h"
 
+#include "absl/memory/memory.h"
+
 namespace webrtc {
 
+std::unique_ptr<RtcEventLog> RtcEventLog::CreateNull() {
+  return absl::make_unique<RtcEventLogNullImpl>();
+}
+
 bool RtcEventLogNullImpl::StartLogging(
     std::unique_ptr<RtcEventLogOutput> output,
     int64_t output_period_ms) {

logging/rtc_event_log/rtc_event_log_impl.cc

@@ -372,8 +372,4 @@ std::unique_ptr<RtcEventLog> RtcEventLog::Create(
 #endif  // ENABLE_RTC_EVENT_LOG
 }
 
-std::unique_ptr<RtcEventLog> RtcEventLog::CreateNull() {
-  return std::unique_ptr<RtcEventLog>(new RtcEventLogNullImpl());
-}
-
 }  // namespace webrtc