added uma stats to check the usage of media stream audio track audio processing

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 055f7e7711e91fc629341a00effa2b741d257e1c..02b32f882cd324089c050e4020bfda3036705e6c 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -7047,6 +7047,14 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Media.AudioTrackProcessingStates"
+    enum="AudioTrackProcessingStates">
+  <summary>
+    State of the media stream audio track processing, sampled once during the
+    life time of a MediaStreamAudioProcessor.
+  </summary>
+</histogram>
+
 <histogram name="Media.CacheUseful" enum="BooleanSuccess">
   <summary>
     Whether a media response might be used to satisfy a future request.
@@ -25025,6 +25033,11 @@ other types of suffix sets.
   <int value="10" label="k192000Hz"/>
 </enum>
 
+<enum name="AudioTrackProcessingStates" type="int">
+  <int value="0" label="Enabled"/>
+  <int value="1" label="Disabled"/>
+</enum>
+
 <enum name="AutocheckoutBubble" type="int">
   <obsolete>
     Deprecated as of 8/2013.