[fix] use shared ptr to create real time clock

src/qos/clock.cc

@@ -60,4 +60,8 @@ Clock* Clock::GetRealTimeClock() {
   static Clock* const clock = new RealTimeClock();
   return clock;
 }
+
+std::shared_ptr<Clock> Clock::GetRealTimeClockShared() {
+  return std::make_shared<RealTimeClock>();
+}
 }  // namespace webrtc

src/qos/clock.h

@@ -66,6 +66,7 @@ class Clock {
 
   // Returns an instance of the real-time system clock implementation.
   static Clock* GetRealTimeClock();
+  static std::shared_ptr<Clock> GetRealTimeClockShared();
 };
 
 }  // namespace webrtc