Make OS audio buffer size limits visible.

media/base/audio_latency.cc

 // Copyright 2016 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/audio_latency.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
+#include "media/base/limits.h"
 
 namespace media {
 
 namespace {
 #if !defined(OS_WIN)
 // Taken from "Bit Twiddling Hacks"
 // http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
 uint32_t RoundUpToPowerOfTwo(uint32_t v) {
   v--;
   v |= v >> 1;
@@ skipping 101 matching lines @@
 #endif
 
   return hardware_buffer_size;
 }
 
 int AudioLatency::GetExactBufferSize(base::TimeDelta duration,
                                      int sample_rate,
                                      int hardware_buffer_size) {
   const double requested_buffer_size = duration.InSecondsF() * sample_rate;
 
+  // On OSX the preferred buffer size is larger than the minimum, however we
+  // allow values down to the minimum if requested explicitly.
+#if defined(OS_MACOSX)
+  hardware_buffer_size = limits::kMinimumOutputBufferSize;
+#endif
+
   DCHECK_NE(0, hardware_buffer_size);
 
   // Round the requested size to the nearest multiple of the hardware size
   const int buffer_size =
       std::round(std::max(requested_buffer_size, 1.0) / hardware_buffer_size) *
       hardware_buffer_size;
 
-  return std::max(buffer_size, hardware_buffer_size);
+  return std::min(static_cast<int>(media::limits::kMaximumOutputBufferSize),
+                  std::max(buffer_size, hardware_buffer_size));
 }
 
 }  // namespace media