Limit resampling/allocation/locking when using signal processing algorithms from WebRTC.org, since none of that is needed for duplex. We might want to patch upstream to add a template-based policy to be able to skip the locks. We also want to inspect their code to prevent allocations in the callback. Those issues are very apparent when taking a profile of a regular call.

For example, this is useless: http://searchfox.org/mozilla-central/source/media/webrtc/trunk/webrtc/modules/audio_processing/audio_processing_impl.cc#789, but there are a lot of things like that.