Make OS audio buffer size limits visible.

media/audio/audio_manager.h

Index: media/audio/audio_manager.h
diff --git a/media/audio/audio_manager.h b/media/audio/audio_manager.h
index f92651ed0627934de813316751d8b6158b7c66bb..4abdb64611c94edc66172c52449584fa39aa22c8 100644
--- a/media/audio/audio_manager.h
+++ b/media/audio/audio_manager.h
@@ -187,6 +187,11 @@ class MEDIA_EXPORT AudioManager {
   // Limits the number of streams that can be created for testing purposes.
   virtual void SetMaxStreamCountForTesting(int max_input, int max_output);
 
+  // Get the minimum and maximum audio buffer sizes. The definitions exist in
+  // the specific AudioManager implementations.
+  static int GetMinimumAudioBufferSize(int sample_rate);
+  static int GetMaximumAudioBufferSize(int sample_rate);
+
  protected:
   FRIEND_TEST_ALL_PREFIXES(AudioManagerTest, AudioDebugRecording);
   friend class AudioDeviceInfoAccessorForTests;