Update to current webrtc library

This is from the upstream library commit id
3326535126e435f1ba647885ce43a8f0f3d317eb, corresponding to Chromium
88.0.4290.1.

webrtc/modules/audio_processing/level_estimator.cc

@@ -0,0 +1,29 @@
+/*
+ *  Copyright (c) 2019 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/level_estimator.h"
+
+#include "api/array_view.h"
+
+namespace webrtc {
+
+LevelEstimator::LevelEstimator() {
+  rms_.Reset();
+}
+
+LevelEstimator::~LevelEstimator() = default;
+
+void LevelEstimator::ProcessStream(const AudioBuffer& audio) {
+  for (size_t i = 0; i < audio.num_channels(); i++) {
+    rms_.Analyze(rtc::ArrayView<const float>(audio.channels_const()[i],
+                                             audio.num_frames()));
+  }
+}
+}  // namespace webrtc