Add RTC_ prefix to (D)CHECKs and related macros.

webrtc/video/send_statistics_proxy.cc

Index: webrtc/video/send_statistics_proxy.cc
diff --git a/webrtc/video/send_statistics_proxy.cc b/webrtc/video/send_statistics_proxy.cc
index e60614c9b653b30fd546e7deec1c4c875f0ea5b0..505dc07ab7bb8f418fe567cea3b9f7cd695b7220 100644
--- a/webrtc/video/send_statistics_proxy.cc
+++ b/webrtc/video/send_statistics_proxy.cc
@@ -225,8 +225,8 @@ void SendStatisticsProxy::DataCountersUpdated(
     uint32_t ssrc) {
   rtc::CritScope lock(&crit_);
   VideoSendStream::StreamStats* stats = GetStatsEntry(ssrc);
-  DCHECK(stats != nullptr) << "DataCountersUpdated reported for unknown ssrc: "
-                           << ssrc;
+  RTC_DCHECK(stats != nullptr)
+      << "DataCountersUpdated reported for unknown ssrc: " << ssrc;
 
   stats->rtp_stats = counters;
 }