Boost WaveOut thread priority for background audio.

media/audio/win/waveout_output_win.cc

Index: media/audio/win/waveout_output_win.cc
diff --git a/media/audio/win/waveout_output_win.cc b/media/audio/win/waveout_output_win.cc
index f18b2fa4287dc59c01ed21596f6c6fbb07d28c18..48f41e18f976e3be69015cb385bcae295b0131fc 100644
--- a/media/audio/win/waveout_output_win.cc
+++ b/media/audio/win/waveout_output_win.cc
@@ -11,6 +11,8 @@
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
+#include "base/message_loop_proxy.h"
+#include "base/threading/platform_thread.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_util.h"
 #include "media/audio/win/audio_manager_win.h"
@@ -108,6 +110,11 @@ PCMWaveOutAudioOutputStream::PCMWaveOutAudioOutputStream(
   }
   format_.SubFormat = KSDATAFORMAT_SUBTYPE_PCM;
   format_.Samples.wValidBitsPerSample = params.bits_per_sample();
+
+  // Boost thread priority.  Required for glitch free background audio.

[scherkus (not reviewing), 2012/11/30 22:13:34]

which thread is this?

the OS callback thread or a chrome-created thread?

do we need to call this every invocation of BufferCallback()?

[henrika (OOO until Aug 14), 2012/12/03 08:35:43]

Same question as Andrew.

[DaleCurtis, 2012/12/03 18:11:06]

Henrik, please see the old messages for full discussion, but this is the thread
we create in the audio manager, hence the dcheck.

+  DCHECK(manager_->GetMessageLoop()->BelongsToCurrentThread());
+  base::PlatformThread::SetThreadPriority(
+      GetCurrentThread(), base::kThreadPriority_RealtimeAudio);
 }
 
 PCMWaveOutAudioOutputStream::~PCMWaveOutAudioOutputStream() {