AEC3: Adding default AEC3 configurations that are setup specific

This adds functionality to AEC3 to produce setup-specific
default configurations that are tailored to work well for the
number of channels at hand.

The tunings are only used for the case when no echo control factory
has been provided.

Bug: webrtc:11151,chromium:1029717
Change-Id: I1bd2d10327300c7b0f3169a52bf66700b781fd6b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/161086
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29972}
diff --git a/modules/audio_processing/audio_processing_impl.h b/modules/audio_processing/audio_processing_impl.h
index 5f1d12f..e5d0573 100644
--- a/modules/audio_processing/audio_processing_impl.h
+++ b/modules/audio_processing/audio_processing_impl.h
@@ -153,6 +153,7 @@
   std::unique_ptr<ApmDataDumper> data_dumper_;
   static int instance_count_;
   const bool enforced_usage_of_legacy_ns_;
+  const bool use_setup_specific_default_aec3_config_;
 
   SwapQueue<RuntimeSetting> capture_runtime_settings_;
   SwapQueue<RuntimeSetting> render_runtime_settings_;