Remove ignored return code from modules.

ModuleProcessImpl doesn't act on return codes and having them around is
confusing (it's unclear what an error return code here would do even).

BUG=
R=tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1703833002 .

Cr-Commit-Position: refs/heads/master@{#11747}

webrtc/modules/rtp_rtcp/source/receive_statistics_impl.cc

@@ -454,14 +454,13 @@ void ReceiveStatisticsImpl::SetMaxReorderingThreshold(
   }
 }
 
-int32_t ReceiveStatisticsImpl::Process() {
+void ReceiveStatisticsImpl::Process() {
   CriticalSectionScoped cs(receive_statistics_lock_.get());
   for (StatisticianImplMap::iterator it = statisticians_.begin();
        it != statisticians_.end(); ++it) {
     it->second->ProcessBitrate();
   }
   last_rate_update_ms_ = clock_->TimeInMilliseconds();
-  return 0;
 }
 
 int64_t ReceiveStatisticsImpl::TimeUntilNextProcess() {
@@ -530,7 +529,7 @@ void NullReceiveStatistics::SetMaxReorderingThreshold(
 
 int64_t NullReceiveStatistics::TimeUntilNextProcess() { return 0; }
 
-int32_t NullReceiveStatistics::Process() { return 0; }
+void NullReceiveStatistics::Process() {}
 
 void NullReceiveStatistics::RegisterRtcpStatisticsCallback(
     RtcpStatisticsCallback* callback) {}

webrtc/modules/rtp_rtcp/source/receive_statistics_impl.h

@@ -112,7 +112,7 @@ class ReceiveStatisticsImpl : public ReceiveStatistics,
   void SetMaxReorderingThreshold(int max_reordering_threshold) override;
 
   // Implement Module.
-  int32_t Process() override;
+  void Process() override;
   int64_t TimeUntilNextProcess() override;
 
   void RegisterRtcpStatisticsCallback(

webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc

@@ -118,7 +118,7 @@ int64_t ModuleRtpRtcpImpl::TimeUntilNextProcess() {
 }
 
 // Process any pending tasks such as timeouts (non time critical events).
-int32_t ModuleRtpRtcpImpl::Process() {
+void ModuleRtpRtcpImpl::Process() {
   const int64_t now = clock_->TimeInMilliseconds();
   last_process_time_ = now;
 
@@ -202,7 +202,6 @@ int32_t ModuleRtpRtcpImpl::Process() {
     // A receiver has timed out
     rtcp_receiver_.UpdateTMMBR();
   }
-  return 0;
 }
 
 void ModuleRtpRtcpImpl::SetRtxSendStatus(int mode) {

webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.h

@@ -35,7 +35,7 @@ class ModuleRtpRtcpImpl : public RtpRtcp {
   int64_t TimeUntilNextProcess() override;
 
   // Process any pending tasks such as timeouts.
-  int32_t Process() override;
+  void Process() override;
 
   // Receiver part.