[Relanding] Fixes bug in Media.AudioInputCbErrorMac histogram.

See https://codereview.chromium.org/702453003/ for the initial patch.

This is a new attempt to land but this time without NOTREACHED since it broke some WebRTC tests.

TBR=tommi
BUG=428706

Review URL: https://codereview.chromium.org/705553002

Cr-Commit-Position: refs/heads/master@{#302602}

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/sparse_histogram.h"
 #include "media/audio/mac/audio_manager_mac.h"
 #include "media/base/audio_bus.h"
 #include "media/base/data_buffer.h"
@@ -496,8 +497,10 @@ OSStatus AUAudioInputStream::InputProc(void* user_data,
                                     bus_number,
                                     number_of_frames,
                                     audio_input->audio_buffer_list());
-  if (result)
+  if (result) {
+    UMA_HISTOGRAM_SPARSE_SLOWLY("Media.AudioInputCbErrorMac", result);
     return result;
+  }
 
   // Deliver recorded data to the consumer as a callback.
   return audio_input->Provide(number_of_frames,