Make OS audio buffer size limits visible.

media/base/limits.h

 // Copyright (c) 2011 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.
 
 // Contains limit definition constants for the media subsystem.
 
 #ifndef MEDIA_BASE_LIMITS_H_
 #define MEDIA_BASE_LIMITS_H_
 
+#include "build/build_config.h"
+
 namespace media {
 
 namespace limits {
 
 enum {
   // Maximum possible dimension (width or height) for any video.
   kMaxDimension = (1 << 15) - 1,  // 32767
 
   // Maximum possible canvas size (width multiplied by height) for any video.
   kMaxCanvas = (1 << (14 * 2)),  // 16384 x 16384
@@ skipping 31 matching lines @@
   // lengths are somewhat arbitrary as the EME spec doesn't specify any limits.
   kMinCertificateLength = 128,
   kMaxCertificateLength = 16 * 1024,
   kMaxSessionIdLength = 512,
   kMinKeyIdLength = 1,
   kMaxKeyIdLength = 512,
   kMaxKeyIds = 128,
   kMaxInitDataLength = 64 * 1024,         // 64 KB
   kMaxSessionResponseLength = 64 * 1024,  // 64 KB
   kMaxKeySystemLength = 256,
+
+// Minimum and maximum buffer sizes for certain audio platforms.
+#if defined(OS_MACOSX)
+  // Values taken from AudioManagerMac.

[DaleCurtis, 2017/06/27 17:25:08]

This is now the source of these values, so no need to list where they came from.

[Andrew MacPherson, 2017/06/27 17:46:49]

Done.

+  kMinAudioBufferSize = 128,
+  kMaxAudioBufferSize = 4096,
+#elif defined(USE_PULSEAUDIO)
+  // Values taken from AudioManagerPulse.
+  kMinAudioBufferSize = 512,
+  kMaxAudioBufferSize = 8192,
+#elif defined(USE_CRAS)
+  // Values taken from AudioManagerCras, though the minimum was dropped from 512
+  // to 256 to allow explicitly requesting this buffer size on any board.
+  kMinAudioBufferSize = 256,
+  kMaxAudioBufferSize = 8192,
+#endif
 };
 
 }  // namespace limits
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_LIMITS_H_