Make OS audio buffer size limits visible.

media/audio/cras/audio_manager_cras.cc

Index: media/audio/cras/audio_manager_cras.cc
diff --git a/media/audio/cras/audio_manager_cras.cc b/media/audio/cras/audio_manager_cras.cc
index 2e6d346e73bb1d47d5c343911e4bcb6417d079ac..17526cd12163efb7dbf85bdfaa0193d292a95cc2 100644
--- a/media/audio/cras/audio_manager_cras.cc
+++ b/media/audio/cras/audio_manager_cras.cc
@@ -40,10 +40,6 @@ const int kMaxOutputStreams = 50;
 // Default sample rate for input and output streams.
 const int kDefaultSampleRate = 48000;
 
-// Define bounds for the output buffer size.
-const int kMinimumOutputBufferSize = 512;
-const int kMaximumOutputBufferSize = 8192;
-
 // Default input buffer size.
 const int kDefaultInputBufferSize = 1024;
 
@@ -308,7 +304,7 @@ int AudioManagerCras::GetMinimumOutputBufferSizePerBoard() {
     return 768;
   else if (board == "samus")
     return 256;
-  return kMinimumOutputBufferSize;
+  return 512;
 }
 
 AudioParameters AudioManagerCras::GetPreferredOutputStreamParameters(
@@ -323,8 +319,9 @@ AudioParameters AudioManagerCras::GetPreferredOutputStreamParameters(
     bits_per_sample = input_params.bits_per_sample();
     channel_layout = input_params.channel_layout();
     buffer_size =
-        std::min(kMaximumOutputBufferSize,
-                 std::max(buffer_size, input_params.frames_per_buffer()));
+        std::min(static_cast<int>(limits::kMaxAudioBufferSize),
+                 std::max(static_cast<int>(limits::kMinAudioBufferSize),

[o1ka, 2017/06/29 15:29:58]

rtoy@: Do we need a "buffer size is below recommended" UMA stat to track the
usage of this feature?

+                          input_params.frames_per_buffer()));
   }
 
   int user_buffer_size = GetUserBufferSize();