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..88c1751e311c066f73b8234ecdde4c25013d9b1b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -21868,6 +21868,22 @@ 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
+    renderer buffer size is a multiply of system buffer size, and render calls

[Ilya Sherman, 2016/08/27 06:38:45]

nit: s/multiply/multiple (throughout)

[o1ka, 2016/08/29 15:52:17]

Done.

+    from browser to renderer are issued evenly. When -1, it means the renderer
+    buffer sizes is larger than system buffer size, but is not an exact multiply

[Ilya Sherman, 2016/08/27 06:38:45]

nit: s/sizes/size

[o1ka, 2016/08/29 15:52:17]

Done.

+    of it; in this case browser periodically skips a call to renderer. When
+    positive, floor(value/2) reflects the number of extra consecutive render
+    requests issued by browser to renderer each time to fulfill the system audio
+    render request; if (value/2) is not integer, then plus one more extra call
+    is issued periodically.
+  </summary>
+</histogram>
+
 <histogram name="Media.Audio.Render.FramesRequested" units="frames">
   <owner>tommi@chromium.org</owner>
   <summary>
@@ -97297,6 +97313,14 @@ 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" label="Exact latency in milliseconds"/>
+  <suffix name="LatencyInteractive" label="Interactive latency"/>
+  <suffix name="LatencyRtc" label="RTC latency"/>
+  <suffix name="LatencyPlayback" label="Playback latency"/>
+  <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"/>