diff --git a/webrtc/system_wrappers/include/metrics.h b/webrtc/system_wrappers/include/metrics.h
index 25a51807de..e84e8ecd4d 100644
--- a/webrtc/system_wrappers/include/metrics.h
+++ b/webrtc/system_wrappers/include/metrics.h
@@ -58,6 +58,9 @@
 // };
 //
 // RTC_HISTOGRAM_ENUMERATION("WebRTC.Types", kTypeX, kBoundary);
+//
+// NOTE: It is recommended to do the Chromium review for modifications to
+// histograms.xml before new metrics are committed to WebRTC.
 
 
 // Macros for adding samples to a named histogram.