Redesign of the render buffering in AEC3

This CL centralizes the render buffering in AEC3 so that all render
buffers are updated and synchronized/aligned with the render alignment
buffer.

Bug: webrtc:8597, chromium:790905
Change-Id: I8a94e5c1f27316b6100b420eec9652ea31c1a91d
Reviewed-on: https://webrtc-review.googlesource.com/25680
Commit-Queue: Per Åhgren <peah@webrtc.org>
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20989}

modules/audio_processing/aec3/vector_buffer.cc

@@ -0,0 +1,26 @@
+/*
+ *  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 "modules/audio_processing/aec3/vector_buffer.h"
+
+#include "modules/audio_processing/aec3/aec3_common.h"
+
+namespace webrtc {
+
+VectorBuffer::VectorBuffer(size_t size, size_t height)
+    : size(size), buffer(size, std::vector<float>(height, 0.f)) {
+  for (auto& c : buffer) {
+    std::fill(c.begin(), c.end(), 0.f);
+  }
+}
+
+VectorBuffer::~VectorBuffer() = default;
+
+}  // namespace webrtc