Add --waveout-buffers switch for Windows users.

media/audio/audio_util.cc

 // Copyright (c) 2012 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.
 
 // Software adjust volume of samples, allows each audio stream its own
 // volume without impacting master volume for chrome and other applications.
 
 // Implemented as templates to allow 8, 16 and 32 bit implementations.
 // 8 bit is unsigned and biased by 128.
 
@@ skipping 321 matching lines @@
          samples * base::Time::kMillisecondsPerSecond <
          sample_rate * kMillisecondsPerHardwarePacket) {
     samples *= 2;
   }
   return samples;
 }
 
 #if defined(OS_WIN)
 
 int NumberOfWaveOutBuffers() {
+  // Use the user provided buffer count if provided.
+  int buffers = 0;
+  std::string buffers_str(CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+      switches::kWaveOutBuffers));
+  if (base::StringToInt(buffers_str, &buffers) && buffers > 0) {
+    return buffers;
+  }
+
   // Use 4 buffers for Vista, 3 for everyone else:
   //  - The entire Windows audio stack was rewritten for Windows Vista and wave
   //    out performance was degraded compared to XP.
   //  - The regression was fixed in Windows 7 and most configurations will work
   //    with 2, but some (e.g., some Sound Blasters) still need 3.
   //  - Some XP configurations (even multi-processor ones) also need 3.
   return (base::win::GetVersion() == base::win::VERSION_VISTA) ? 4 : 3;
 }
 
 #endif
 
 }  // namespace media