Major AEC3 render pipeline changes

webrtc/modules/audio_processing/aec3/downsampled_render_buffer.cc

+/*
+ *  Copyright (c) 2017 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.
+ */
+
+#include "webrtc/modules/audio_processing/aec3/downsampled_render_buffer.h"
+
+namespace webrtc {
+
+DownsampledRenderBuffer::DownsampledRenderBuffer() = default;
+
+DownsampledRenderBuffer::~DownsampledRenderBuffer() = default;
+
+}  // namespace webrtc