Clean up histogram'd media enum max values.

media/audio/sample_rates.h

Index: media/audio/sample_rates.h
diff --git a/media/audio/sample_rates.h b/media/audio/sample_rates.h
index 7c29e548b340e385512eedf82821a0f9f15f7060..88f332fc05b8d0b7fbe74815848a489dc4705d72 100644
--- a/media/audio/sample_rates.h
+++ b/media/audio/sample_rates.h
@@ -23,7 +23,9 @@ enum AudioSampleRate {
   k88200Hz = 8,
   k176400Hz = 9,
   k192000Hz = 10,
-  kUnexpectedAudioSampleRate  // Must always be last!
+  kUnexpectedAudioSampleRate,
+  kAudioSampleRateMax =

[rileya (GONE FROM CHROMIUM), 2014/01/29 19:24:11]

This is a little iffy -- kUnexpectedAudioSampleRate sounds like a meaningful
value, but it's also used as the histogram cap. I added a max value to be
consistent with everything else, but adding a '+1' in the uma call seems
unnecessary if kUnexpectedAudioSampleRate was already used there...

[Ami GONE FROM CHROMIUM, 2014/01/29 21:29:02]

kUnexpected is a terrible fit since it doesn't get reported to UMA (hence the
weirdness w/ no explicit value and expected to change value if new rates are
added above it, even though this is a UMA-reported stat so should "never
change").
IMO set kAudioSampleRateMax = k192000Hz, drop kUnexpected, and take the hit on
changing
AudioSampleRate AsAudioSampleRate(int sample_rate);
to
bool ToAudioSampleRate(int sample_rate, AudioSampleRate* asr);
and return false if unexpected.

+      kUnexpectedAudioSampleRate,  // Must always equal last entry!

[Ami GONE FROM CHROMIUM, 2014/01/29 21:29:02]

FWIW, here and elsewhere, the real requirement (for UMA) is that this equal the
largest value ever used.  

 };
 
 // Helper method to convert integral values to their respective enum values,