Clean up histogram'd media enum max values.

media/audio/sample_rates.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_AUDIO_SAMPLE_RATES_H_
 #define MEDIA_AUDIO_SAMPLE_RATES_H_
 
 #include "media/base/media_export.h"
 
 namespace media {
 
 // Enumeration used for histogramming sample rates into distinct buckets.
 // Logged to UMA, so never reuse a value, always add new/greater ones!
 enum AudioSampleRate {
   k8000Hz = 0,
   k16000Hz = 1,
   k32000Hz = 2,
   k48000Hz = 3,
   k96000Hz = 4,
   k11025Hz = 5,
   k22050Hz = 6,
   k44100Hz = 7,
   k88200Hz = 8,
   k176400Hz = 9,
   k192000Hz = 10,
-  kUnexpectedAudioSampleRate  // Must always be last!
+  // Must always equal the largest value ever reported:
+  kAudioSampleRateMax = k192000Hz,
 };
 
 // Helper method to convert integral values to their respective enum values,
-// or kUnexpectedAudioSampleRate if no match exists.
-MEDIA_EXPORT AudioSampleRate AsAudioSampleRate(int sample_rate);
+// returns false for unexpected sample rates.
+MEDIA_EXPORT bool ToAudioSampleRate(int sample_rate, AudioSampleRate* asr);
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_SAMPLE_RATES_H_