Add support for real-time audio threads.

base/threading/platform_thread.h

Index: base/threading/platform_thread.h
===================================================================
--- base/threading/platform_thread.h	(revision 83935)
+++ base/threading/platform_thread.h	(working copy)
@@ -91,6 +91,10 @@
   // |thread_handle|.
   static void Join(PlatformThreadHandle thread_handle);
 
+  // Enables time-contraint policy and priority suitable for low-latency,
+  // glitch-resistant audio.
+  static void EnableRealtimeAudioPerformance(PlatformThreadHandle handle);

[Ken Russell (switch to Gerrit), 2011/05/09 22:28:14]

An audio-specific method seems out of place in this low-level class. Can you
think of a different way to name or specify this that would have the same
effect? For example, what about passing in the time constraint parameters in
some form, which might be ignored on other operating systems, and then name this
method generically? Or what about not making the Mac implementation not quite so
audio-specific, and call it something like "BoostThreadPriority" or
"SetThreadPriorityToRealtime"?

+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformThread);
 };