Revert of Remove ignored return code from modules.

webrtc/video/call_stats.cc

Index: webrtc/video/call_stats.cc
diff --git a/webrtc/video/call_stats.cc b/webrtc/video/call_stats.cc
index 8874c2b6317b7d22d4bec6e007e57c809a53042a..1ee462555299642674c29f371d552ca1697844cc 100644
--- a/webrtc/video/call_stats.cc
+++ b/webrtc/video/call_stats.cc
@@ -109,11 +109,11 @@
   return last_process_time_ + kUpdateIntervalMs - clock_->TimeInMilliseconds();
 }
 
-void CallStats::Process() {
+int32_t CallStats::Process() {
   rtc::CritScope cs(&crit_);
   int64_t now = clock_->TimeInMilliseconds();
   if (now < last_process_time_ + kUpdateIntervalMs)
-    return;
+    return 0;
 
   last_process_time_ = now;
 
@@ -132,6 +132,7 @@
     sum_avg_rtt_ms_ += avg_rtt_ms_;
     ++num_avg_rtt_;
   }
+  return 0;
 }
 
 int64_t CallStats::avg_rtt_ms() const {