Add empty residual echo detector.

webrtc/modules/audio_processing/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("//build/config/arm.gni")
 import("//third_party/protobuf/proto_library.gni")
@@ skipping 81 matching lines @@
     "level_controller/saturating_gain_estimator.h",
     "level_controller/signal_classifier.cc",
     "level_controller/signal_classifier.h",
     "level_estimator_impl.cc",
     "level_estimator_impl.h",
     "logging/apm_data_dumper.cc",
     "logging/apm_data_dumper.h",
     "noise_suppression_impl.cc",
     "noise_suppression_impl.h",
     "render_queue_item_verifier.h",
+    "residual_echo_detector.cc",
+    "residual_echo_detector.h",
     "rms_level.cc",
     "rms_level.h",
     "splitting_filter.cc",
     "splitting_filter.h",
     "three_band_filter_bank.cc",
     "three_band_filter_bank.h",
     "transient/common.h",
     "transient/daubechies_8_wavelet_coeffs.h",
     "transient/dyadic_decimator.h",
     "transient/moving_moments.cc",
@@ skipping 330 matching lines @@
         "test/protobuf_utils.cc",
         "test/protobuf_utils.h",
       ]
 
       deps = [
         ":audioproc_debug_proto",
       ]
     }
   }
 }