Autoplay experiment metric fixes and additions.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 1b0350e83608e43b1ba7b675dd0810bffd312e1b..9eea479c3673cbe327d57283bc681e654feff7ed 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -68059,6 +68059,14 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="11" label="Any playback started."/>
   <int value="12" label="Any playback paused."/>
   <int value="13" label="Any playback bailed out."/>
+  <int value="14" label="Any playback completed."/>
+  <int value="15" label="Any media element encountered."/>
+  <int value="16" label="Any video element encountered."/>
+  <int value="17" label="Autoplayed media complete."/>
+  <int value="18" label="Initial play with user gesture."/>
+  <int value="19" label="Initial play during user gesture."/>
+  <int value="20" label="Initial play without user gesture."/>
+  <int value="21" label="Initial play not during user gesture."/>
 </enum>
 
 <enum name="MediaGalleriesUsageType" type="int">