AEC3: Add flag for requiring a high pass filter effect before the AEC

Bug: webrtc:11159, chromium:1030179
Change-Id: Ic6b686a36efa433156a66252394fa551b8ed1837
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/161227
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29986}
diff --git a/modules/audio_processing/include/audio_processing.h b/modules/audio_processing/include/audio_processing.h
index 539871d..8b0dce9 100644
--- a/modules/audio_processing/include/audio_processing.h
+++ b/modules/audio_processing/include/audio_processing.h
@@ -283,6 +283,7 @@
       // Recommended not to use. Will be removed in the future.
       bool use_legacy_aec = false;
       bool export_linear_aec_output = false;
+      bool enforce_high_pass_filtering = true;
     } echo_canceller;
 
     // Enables background noise suppression.