Change NetEq::GetPlayoutTimestamp to return an rtc::Optional<uint32_t>

webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc

Index: webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc
diff --git a/webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc b/webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc
index d30daaaf3407f6a221d987eca57ba3917429fee8..f9e0d983e0cd980ffc96b32d9fd1c000ed120fd2 100644
--- a/webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc
+++ b/webrtc/modules/audio_coding/acm2/audio_coding_module_impl.cc
@@ -902,8 +902,8 @@ int AudioCodingModuleImpl::DisableOpusDtx() {
   return encoder_stack_->SetDtx(false) ? 0 : -1;
 }
 
-int AudioCodingModuleImpl::PlayoutTimestamp(uint32_t* timestamp) {
-  return receiver_.GetPlayoutTimestamp(timestamp) ? 0 : -1;
+rtc::Optional<uint32_t> AudioCodingModuleImpl::PlayoutTimestamp() {
+  return receiver_.GetPlayoutTimestamp();
 }
 
 bool AudioCodingModuleImpl::HaveValidEncoder(const char* caller_name) const {