UMA stats for browser/renderer audio rendering buffer size mismatch.

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 1e85229ab2098cb3036c58fc450a568310f3df3b..c081b254f4248418449a78f9fd45d61f9852c56c 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -21868,6 +21868,21 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Media.Audio.Render.BufferSizeMismatch">
+  <owner>olka@chromium.org</owner>
+  <summary>
+    Mismatch between the system buffer size the browser side renders audio at
+    and the buffer size it requests from renderer.  When equals zero, it means
+    buffer sizes are equal. When positive, the value reflects the average number
+    of extra consecutive render requests issued by browser to renderer (scaled
+    by a factor of 1000);  any positive values can cause problems for RTC. When
+    negative, it reflects the average number of extra system audio render calls
+    per one request to the renderer (scaled by a factor of 1000). Any values
+    those are not multiples of 1000 mean that from time to time browser skips a
+    call to renderer, which can cause problems for RTC.

[Ilya Sherman, 2016/08/24 22:20:23]

How can you identify values that are not multiples of 1000 when they are scaled
down by a factor of 1000?

[o1ka, 2016/08/25 11:48:34]

They are scaled up, not down. I changed the wording.
Also, I changed the factor to be 100 (though it does not really affect the
number of histogram buckets).

+  </summary>
+</histogram>
+
 <histogram name="Media.Audio.Render.FramesRequested" units="frames">
   <owner>tommi@chromium.org</owner>
   <summary>
@@ -97297,6 +97312,15 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="DefaultBrowser.SetDefaultAsyncDuration"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="AudioLatency" separator=".">
+  <suffix name="LatencyExactMs"/>
+  <suffix name="LatencyInteractive"/>
+  <suffix name="LatencyRtc"/>
+  <suffix name="LatencyPlayback"/>
+  <suffix name="LatencyOther"/>

[Ilya Sherman, 2016/08/24 22:20:23]

Please provide a label for each suffix.

[o1ka, 2016/08/25 11:48:34]

Done.

+  <affected-histogram name="Media.Audio.Render.BufferSizeMismatch"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="AutofillDataAvailability" separator=".">
   <suffix name="WithNoData" label="no autofill data"/>
   <suffix name="WithOnlyServerData" label="only server autofill data"/>