UMA stats for AudioRendererSinkCache utilization.

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 1cf9ce5d7ffe91f579ba6efbdde276681ae02c14..301d3108b3a6e76dc8dfc8252393251f9a656983 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -21297,6 +21297,34 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram
+    name="Media.Audio.Render.SinkCache.GetOutputDeviceInfoCacheUtilization"
+    enum="GetOutputDeviceInfoCacheHit">
+  <owner>olka@chromium.org</owner>
+  <summary>
+    Whether a cached sink was used to get audio output device information, or a
+    new one was created for that.

[jwd, 2016/07/12 14:55:08]

Can you make the last part of this sentence a bit clearer. Maybe just change
"new one" to be "new sink" (assuming that's correct).

[o1ka, 2016/07/12 15:06:04]

Done.

+  </summary>
+</histogram>
+
+<histogram name="Media.Audio.Render.SinkCache.InfoSinkReusedForOutput"
+    enum="BooleanReused">
+  <owner>olka@chromium.org</owner>
+  <summary>
+    When a new sink is created to get output device information, it is cached.
+    This metric shows if such a sink is later reused for audio output or deleted
+    unused after timeout expires.

[jwd, 2016/07/12 14:55:08]

Can you mention when this is logged. Is it logged each time it's used, only on
first use, or only when it expires?

[o1ka, 2016/07/12 15:06:04]

Done.

+  </summary>
+</histogram>
+
+<histogram name="Media.Audio.Render.SinkCache.UsedForSinkCreation"
+    enum="BooleanUsage">
+  <owner>olka@chromium.org</owner>
+  <summary>
+    Whether a sink was created through the sink cache or directly.
+  </summary>
+</histogram>
+
 <histogram name="Media.Audio.RenderFailsWhenBufferSizeChangesMac"
     enum="BooleanChanged">
   <owner>henrika@chromium.org</owner>
@@ -78127,6 +78155,21 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="2" label="Gesture predicted but didn't occur"/>
 </enum>
 
+<enum name="GetOutputDeviceInfoCacheHit" type="int">
+  <int value="0" label="Miss: no cached sink found">
+    Output parmeters for a device are requested, and there is no corresponding
+    sink cached; new sink is created and cached.
+  </int>
+  <int value="1" label="Miss: cannot lookup by session id">
+    If session id is used to specify a device, we always have to create and
+    cache a new sink.
+  </int>
+  <int value="2" label="Hit">
+    Output parmeters for a device are requested, and there is a corresponding
+    sink cached.
+  </int>
+</enum>
+
 <enum name="GetPerfDataOutcome" type="int">
   <int value="0" label="Success.">
     Perf data was collected, parsed and attached to the UMA protobuf