Let PacketSource::NextPacket() return an std::unique_ptr

webrtc/modules/audio_coding/acm2/acm_receive_test_oldapi.cc

Index: webrtc/modules/audio_coding/acm2/acm_receive_test_oldapi.cc
diff --git a/webrtc/modules/audio_coding/acm2/acm_receive_test_oldapi.cc b/webrtc/modules/audio_coding/acm2/acm_receive_test_oldapi.cc
index dc8111daf3b2639726cbb18ce67825a04986086e..025a0e9615e735369237ea72ccb2a3b5d01932db 100644
--- a/webrtc/modules/audio_coding/acm2/acm_receive_test_oldapi.cc
+++ b/webrtc/modules/audio_coding/acm2/acm_receive_test_oldapi.cc
@@ -154,7 +154,7 @@ int AcmReceiveTestOldApi::RegisterExternalReceiveCodec(
 
 void AcmReceiveTestOldApi::Run() {
   for (std::unique_ptr<Packet> packet(packet_source_->NextPacket()); packet;
-       packet.reset(packet_source_->NextPacket())) {
+       packet = packet_source_->NextPacket()) {
     // Pull audio until time to insert packet.
     while (clock_.TimeInMilliseconds() < packet->time_ms()) {
       AudioFrame output_frame;