Make OS audio buffer size limits visible.

media/base/mac/audio_util_mac.cc

+// Copyright (c) 2017 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.
+
+#include "media/base/mac/audio_util_mac.h"
+#include "media/base/limits.h"
+
+namespace media {
+
+namespace audio_util_mac {
+
+int GetMinAudioBufferSizeForSampleRate(int min_buffer_size, int sample_rate) {
+  int buffer_size = min_buffer_size;
+  if (sample_rate > 48000) {
+    // The default buffer size is too small for higher sample rates and may lead
+    // to glitching.  Adjust upwards by multiples of the default size.
+    if (sample_rate <= 96000)
+      buffer_size = 2 * limits::kMinAudioBufferSize;
+    else if (sample_rate <= 192000)
+      buffer_size = 4 * limits::kMinAudioBufferSize;
+  }
+  return buffer_size;
+}
+
+}  // namespace audio_util_mac
+
+}  // namespace media