Add histogram stats for average QP per frame for VP9 (for sent video streams):

webrtc/system_wrappers/include/metrics.h

Index: webrtc/system_wrappers/include/metrics.h
diff --git a/webrtc/system_wrappers/include/metrics.h b/webrtc/system_wrappers/include/metrics.h
index 1576f919107f85141078d462d5e736bcd1e4660a..d5e549285fa33aecd054819e9753f3d17a590006 100644
--- a/webrtc/system_wrappers/include/metrics.h
+++ b/webrtc/system_wrappers/include/metrics.h
@@ -69,6 +69,9 @@
 #define RTC_HISTOGRAM_COUNTS_200(name, sample) \
   RTC_HISTOGRAM_COUNTS(name, sample, 1, 200, 50)
 
+#define RTC_HISTOGRAM_COUNTS_500(name, sample) \
+  RTC_HISTOGRAM_COUNTS(name, sample, 1, 500, 50)
+
 #define RTC_HISTOGRAM_COUNTS_1000(name, sample) \
   RTC_HISTOGRAM_COUNTS(name, sample, 1, 1000, 50)
 
@@ -89,6 +92,9 @@
 #define RTC_LOGGED_HISTOGRAM_COUNTS_200(name, sample) \
   RTC_LOGGED_HISTOGRAM_COUNTS(name, sample, 1, 200, 50)
 
+#define RTC_LOGGED_HISTOGRAM_COUNTS_500(name, sample) \
+  RTC_LOGGED_HISTOGRAM_COUNTS(name, sample, 1, 500, 50)
+
 #define RTC_LOGGED_HISTOGRAM_COUNTS_1000(name, sample) \
   RTC_LOGGED_HISTOGRAM_COUNTS(name, sample, 1, 1000, 50)
 
@@ -175,6 +181,10 @@
   RTC_HISTOGRAMS_COMMON(index, name, sample, \
       RTC_HISTOGRAM_COUNTS(name, sample, 1, 200, 50))
 
+#define RTC_HISTOGRAMS_COUNTS_500(index, name, sample) \
+  RTC_HISTOGRAMS_COMMON(index, name, sample, \
+      RTC_HISTOGRAM_COUNTS(name, sample, 1, 500, 50))
+
 #define RTC_HISTOGRAMS_COUNTS_1000(index, name, sample) \
   RTC_HISTOGRAMS_COMMON(index, name, sample, \
       RTC_HISTOGRAM_COUNTS(name, sample, 1, 1000, 50))
@@ -204,6 +214,10 @@
   RTC_HISTOGRAMS_COMMON(index, name, sample, \
       RTC_LOGGED_HISTOGRAM_COUNTS(name, sample, 1, 200, 50))
 
+#define RTC_LOGGED_HISTOGRAMS_COUNTS_500(index, name, sample) \
+  RTC_HISTOGRAMS_COMMON(index, name, sample, \
+      RTC_LOGGED_HISTOGRAM_COUNTS(name, sample, 1, 500, 50))
+
 #define RTC_LOGGED_HISTOGRAMS_COUNTS_1000(index, name, sample) \
   RTC_HISTOGRAMS_COMMON(index, name, sample, \
       RTC_LOGGED_HISTOGRAM_COUNTS(name, sample, 1, 1000, 50))