Use 3 wave out buffers for all XP configurations (not just single-processor).

media/audio/audio_util.cc

Index: media/audio/audio_util.cc
diff --git a/media/audio/audio_util.cc b/media/audio/audio_util.cc
index 83b927d69c59d8ae7a0d8c7256d8132cea537735..a8ce2b53b1b2ade6aee0d4c602c23b129c53bca2 100644
--- a/media/audio/audio_util.cc
+++ b/media/audio/audio_util.cc
@@ -28,7 +28,6 @@
 #include "media/audio/mac/audio_low_latency_output_mac.h"
 #elif defined(OS_WIN)
 #include "base/command_line.h"
-#include "base/sys_info.h"
 #include "base/win/windows_version.h"
 #include "media/audio/audio_manager_base.h"
 #include "media/audio/win/audio_low_latency_input_win.h"
@@ -542,20 +541,13 @@ bool IsWASAPISupported() {
 }
 
 int NumberOfWaveOutBuffers() {
-  // The entire Windows audio stack was rewritten for Windows Vista, and the
-  // wave out API is simulated on top of new API, so there is noticeable
-  // performance degradation compared to Windows XP. So use 4 buffers for Vista.
-  if (base::win::GetVersion() == base::win::VERSION_VISTA)
-    return 4;
-
-  // Part of regression was apparently fixed in Windows 7, but problems remain
-  // at least with some configurations (compared to XP). So use 3 buffers for
-  // Windows 7 and higher.
-  if (base::win::GetVersion() >= base::win::VERSION_WIN7)
-    return 3;
-
-  // Otherwise (for XP), use 3 buffers on single-core systems and 2 otherwise.
-  return (base::SysInfo::NumberOfProcessors() < 2) ? 3 : 2;
+  // 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