I would think you would activate whatever audio device you wanted (either Render or Capture) using CoreAudio API and that would be picked up by the HTML 5 app.
http://msdn.microsoft.com/en-us/library ... 02(v=vs.85).aspx
If that device is activated, then the default device would not be used, I would think it would pick up the activated device for that session.
So no changed to the CEF, changes to your application running the CEF.
This is just a guess, I've switched audio devices in applications using CoreAudio API, but never for an HTML 5 app.
Oh CoreAudio API is vista or later, XP will be Mixer API.
CoreDump