Web MIDI: add a new UMA entry for the final result code

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 ea110b9d7b4be2b0f7cfa6091f0e96200de9f0d0..79e5c7c961d992f8813d51da05c8581b70d47cae 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -17275,6 +17275,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Midi.ResultOnShutdown" enum="MidiResult">
+  <owner>toyoshim@chromium.org</owner>
+  <summary>
+    The final result code of MidiManager on browser shutdown.

[yhirano, 2015/07/07 07:05:21]

[optional] I like "final status".

[Takashi Toyoshima, 2015/07/09 05:02:54]

Done.

+  </summary>
+</histogram>
+
 <histogram name="Mist.SwitchResult" enum="MistSwitchResult">
   <owner>benchan@chromium.org</owner>
   <summary>
@@ -61323,6 +61330,13 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="1" label="Not muted"/>
 </enum>
 
+<enum name="MidiResult" type="int">
+  <int value="0" label="Not initialized"/>
+  <int value="1" label="Succeeded"/>

[yhirano, 2015/07/07 07:05:21]

[optional] successfully initialized?

[Takashi Toyoshima, 2015/07/09 05:02:54]

Done.

+  <int value="2" label="Not supported"/>
+  <int value="3" label="Generic initialization error"/>
+</enum>
+
 <enum name="MigrationNssToPemNetworkTypes" type="int">
   <int value="0" label="EAP"/>
   <int value="1" label="OpenVPN"/>