Add a NOTREACHED and uma stat when the audio callback fails

media/audio/mac/audio_low_latency_input_mac.cc

Index: media/audio/mac/audio_low_latency_input_mac.cc
diff --git a/media/audio/mac/audio_low_latency_input_mac.cc b/media/audio/mac/audio_low_latency_input_mac.cc
index 2b2ce0090da0f54d25fdb9a40f60eb5e7f417b14..ee04f1b6214b9e634d2b1b558731e06deb5fe696 100644
--- a/media/audio/mac/audio_low_latency_input_mac.cc
+++ b/media/audio/mac/audio_low_latency_input_mac.cc
@@ -9,6 +9,7 @@
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/mac/mac_logging.h"
+#include "base/metrics/histogram.h"
 #include "media/audio/mac/audio_manager_mac.h"
 #include "media/base/audio_bus.h"
 #include "media/base/data_buffer.h"
@@ -496,8 +497,11 @@ OSStatus AUAudioInputStream::InputProc(void* user_data,
                                     bus_number,
                                     number_of_frames,
                                     audio_input->audio_buffer_list());
-  if (result)
+  if (result) {
+    UMA_HISTOGRAM_COUNTS("Media.AudioInputCbErrorMac", result);
+    NOTREACHED();
     return result;
+  }
 
   // Deliver recorded data to the consumer as a callback.
   return audio_input->Provide(number_of_frames,