Add multi-channel support to AECM

AECM only supports up to two capture channels, this CL extends it to arbitrary channel counts.

Bug: webrtc:10859
Change-Id: Id56ca633cd9de706fa1254bfa8153de88de0ef70
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/160340
Reviewed-by: Per Ã…hgren <peah@webrtc.org>
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29880}
diff --git a/modules/audio_processing/echo_control_mobile_impl.h b/modules/audio_processing/echo_control_mobile_impl.h
index 718819d..f12ce2a 100644
--- a/modules/audio_processing/echo_control_mobile_impl.h
+++ b/modules/audio_processing/echo_control_mobile_impl.h
@@ -79,7 +79,7 @@
 
   std::vector<std::unique_ptr<Canceller>> cancellers_;
   std::unique_ptr<StreamProperties> stream_properties_;
-  std::array<std::array<int16_t, 160>, 2> low_pass_reference_;
+  std::vector<std::array<int16_t, 160>> low_pass_reference_;
   bool reference_copied_ = false;
 };
 }  // namespace webrtc