Add UMA metrics for VideoCodec.MP4 and VideoCodec.WebM

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 d476b29069e83525241378e66c58b9d231e3693f..3b8efe07baf1448a339c67cc256bd4444f35b9b5 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -27825,6 +27825,22 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Media.MSE.VideoCodec.MP4" enum="MSECodec">
+  <owner>media-dev@chromium.org</owner>
+  <summary>
+    Video codec used in Media Source Extensions playback if the media container
+    is MP4. Set when AddId() is called during playback.
+  </summary>
+</histogram>
+
+<histogram name="Media.MSE.VideoCodec.WebM" enum="MSECodec">
+  <owner>media-dev@chromium.org</owner>
+  <summary>
+    Video codec used in Media Source Extensions playback if the media container
+    is WebM. Set when AddId() is called during playback.
+  </summary>
+</histogram>
+
 <histogram name="Media.Netflix.AudioBitrate" units="kbps">
   <obsolete>
     Deprecated 04/2016 as doesn't have data nor owner.
@@ -28191,6 +28207,22 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Media.SRC.VideoCodec.MP4" enum="VideoCodec">
+  <owner>media-dev@chromium.org</owner>
+  <summary>
+    Video codec used in plain src= (not MSE) HTML5 media if the media container
+    is MP4.
+  </summary>
+</histogram>
+
+<histogram name="Media.SRC.VideoCodec.WebM" enum="VideoCodec">
+  <owner>media-dev@chromium.org</owner>
+  <summary>
+    Video codec used in plain src= (not MSE) HTML5 media if the media container
+    is WebM.
+  </summary>
+</histogram>
+
 <histogram base="true" name="Media.Timeline.DragGestureDuration" units="ms">
 <!-- Name completed by histogram_suffixes name="MediaTimelineWidths" -->