Piggybacking simulcast id and ALR experiment id into video content type extension.

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 f22cf8f1665e3c27c86ba825ffb8d7d6840ded12..ee4506b5aa47fef517a51dd5f6887bab32643da0 100644
--- a/webrtc/system_wrappers/include/metrics.h
+++ b/webrtc/system_wrappers/include/metrics.h
@@ -188,23 +188,37 @@
       RTC_HISTOGRAM_PERCENTAGE(name, sample))
 
 #define RTC_HISTOGRAMS_COMMON(index, name, sample, macro_invocation) \
-  do { \
-    switch (index) { \
-      case 0: \
-        macro_invocation; \
-        break; \
-      case 1: \
-        macro_invocation; \
-        break; \
-      case 2: \
-        macro_invocation; \
-        break; \
-      default: \
-        RTC_NOTREACHED(); \
-    } \
+  do {                                                               \
+    switch (index) {                                                 \
+      case 0:                                                        \
+        macro_invocation;                                            \
+        break;                                                       \
+      case 1:                                                        \
+        macro_invocation;                                            \
+        break;                                                       \
+      case 2:                                                        \
+        macro_invocation;                                            \
+        break;                                                       \
+      case 3:                                                        \
+        macro_invocation;                                            \
+        break;                                                       \
+      case 4:                                                        \
+        macro_invocation;                                            \
+        break;                                                       \
+      case 5:                                                        \
+        macro_invocation;                                            \
+        break;                                                       \
+      case 6:                                                        \
+        macro_invocation;                                            \
+        break;                                                       \
+      case 7:                                                        \
+        macro_invocation;                                            \
+        break;                                                       \
+      default:                                                       \
+        RTC_NOTREACHED();                                            \
+    }                                                                \
   } while (0)
 
-
 namespace webrtc {
 namespace metrics {