Adds Media.Audio.InputDevicePropertyChangedMac UMA stat on Mac

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 bce3cf4240b395184f3558969d262fe2d373322b..f019c8ce491776b17e6db339acfbd6ce3215167f 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -18932,6 +18932,27 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Media.Audio.InputDevicePropertyChangedMac"
+    enum="AudioDevicePropertyResult">
+  <owner>henrika@chromium.org</owner>
+  <summary>
+    Lists device properties that have been changed during an audio input stream
+    session. We update a map of different property changes during a session and
+    all these values are uploaded when an AUAudioInputStream object is closed,

[Ilya Sherman, 2016/02/23 18:45:52]

nit: s/uploaded/recorded

[henrika (OOO until Aug 14), 2016/02/24 09:49:46]

Done.

+    hence multiple enum values can be emitted when the histogram is stored.
+  </summary>
+</histogram>
+
+<histogram name="Media.Audio.InputDevicePropertyChangedStartupFailedMac"
+    enum="AudioDevicePropertyResult">
+  <owner>henrika@chromium.org</owner>
+  <summary>
+    Lists device properties that have been changed during an audio input stream
+    session. Only sampled when Media.Audio.InputStartupSuccessMac reports
+    'Failure' and multiple enum values can be emitted each time that happens.
+  </summary>
+</histogram>
+
 <histogram name="Media.Audio.InputStartupSuccessMac" enum="BooleanSuccess">
   <owner>henrika@chromium.org</owner>
   <summary>
@@ -58338,6 +58359,22 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="16" label="kCodecAC3"/>
 </enum>
 
+<enum name="AudioDevicePropertyResult" type="int">
+  <int value="0" label="Other"/>
+  <int value="1" label="Device has changed"/>
+  <int value="2" label="IO stopped abnormally"/>
+  <int value="3" label="Hog mode"/>
+  <int value="4" label="Bufer frame size"/>
+  <int value="5" label="Buffer frame size range"/>
+  <int value="6" label="Stream configuration"/>
+  <int value="7" label="Actual sample rate"/>
+  <int value="8" label="Nominal sample rate"/>
+  <int value="9" label="Device is running somewhere"/>
+  <int value="10" label="Device is running"/>
+  <int value="11" label="Device is alive"/>
+  <int value="12" label="Stream physical format"/>
+</enum>
+
 <enum name="AudioFramesPerBuffer" type="int">
   <int value="0" label="k160"/>
   <int value="1" label="k320"/>