Add AudioOutputController trace events and UMA backed wedge detection.

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 b4e49225ce51d10ce45a7ebd64945aac6ecb33e2..cbe6839fcf0831ca3c4918f199b97290ddb0e65a 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -5834,6 +5834,11 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Media.AudioOutputControllerWedgeDetected"
+    enum="BooleanSuccess">
+  <summary>Whether a wedge was detected during audio playback or not.</summary>

[jar (doing other things), 2013/11/04 07:03:43]

It is hard to tell if "success" or "failure" means had a wedge or not.

You might choose a better custom enum, or choose an enum that is "true" vs
"false"  and then get rid of the confusing prose "...or not." that you used
above.

[DaleCurtis, 2013/11/04 18:57:32]

I'm always confused with BooleanSuccess when recording "bad" things.  I could
rename this something like "PlaybackStartupSuccess" which might make it clearer.

[Alexei Svitkine (slow), 2013/11/04 22:20:24]

If BooleanSuccess is a bad description, please do switch to a different enum
(adding it if necessary).

In this description, could you clarify what a wedge is e.g. in parentheses after
that word.

[DaleCurtis, 2013/11/04 22:23:52]

I've renamed it completely in the latest patchset. PTAL.

+</histogram>
+
 <histogram name="Media.AudioRendererEvents" enum="AudioRendererEvents">
   <summary>Captures statistics for various AudioRendererImpl events.</summary>
 </histogram>