Make OS audio buffer size limits visible.

media/base/limits.h

Index: media/base/limits.h
diff --git a/media/base/limits.h b/media/base/limits.h
index f936c8bf9257a064c9aeac0229bec51a65ffcb15..2a73c5999caa5c64e63f46720e922598c9dd8b39 100644
--- a/media/base/limits.h
+++ b/media/base/limits.h
@@ -7,6 +7,8 @@
 #ifndef MEDIA_BASE_LIMITS_H_
 #define MEDIA_BASE_LIMITS_H_
 
+#include "build/build_config.h"
+
 namespace media {
 
 namespace limits {
@@ -58,6 +60,17 @@ enum {
   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)
+  kMinAudioBufferSize = 128,
+  kMaxAudioBufferSize = 4096,
+#elif defined(USE_CRAS)
+  // Though CRAS has different per-board defaults, allow explicitly requesting
+  // this buffer size on any board.
+  kMinAudioBufferSize = 256,
+  kMaxAudioBufferSize = 8192,
+#endif
 };
 
 }  // namespace limits