Record user interactions with MediaSession by action type

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 1fdc8e42831faad958d368c6510b164d5373a9d0..b29fc79f1fe94bffc539486ba64dab81ce53d260 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -27564,6 +27564,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Media.Session.UserAction" enum="MediaSessionUserAction">
+  <owner>avayvod@chromium.org</owner>
+  <owner>mlamouri@chromium.org</owner>
+  <owner>zqzhang@chromium.org</owner>

[mlamouri (slow - plz ping), 2017/04/07 11:15:56]

Can you just put you and media-dev@chromium.org?

[Zhiqiang Zhang (Slow), 2017/04/07 15:12:43]

Done.

+  <summary>
+    The number of times user interacts with MediaSession sorted by action type.
+  </summary>
+</histogram>
+
 <histogram name="Media.TimeToPipelineStarted" units="ms">
   <obsolete>
     Removed from code 2014/6/18.
@@ -102586,6 +102595,18 @@ from previous Chrome versions.
   <int value="4" label="System Transient Duck"/>
 </enum>
 
+<enum name="MediaSessionUserAction" type="int">
+  <int value="0" label="Play"/>
+  <int value="1" label="Play (default handler)"/>
+  <int value="2" label="Pause"/>
+  <int value="3" label="Pause (default handler)"/>
+  <int value="4" label="Stop (default handler)"/>
+  <int value="5" label="Previous track"/>
+  <int value="6" label="Next track"/>
+  <int value="7" label="Seek backward"/>
+  <int value="8" label="Seek forward"/>
+</enum>
+
 <enum name="MediaStreamRequestResult" type="int">
   <int value="0" label="Ok"/>
   <int value="1" label="Permission Denied"/>