Update to current webrtc library

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

webrtc/api/audio/echo_control.h

@@ -0,0 +1,68 @@
+/*
+ *  Copyright (c) 2018 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.
+ */
+
+#ifndef API_AUDIO_ECHO_CONTROL_H_
+#define API_AUDIO_ECHO_CONTROL_H_
+
+#include <memory>
+
+#include "rtc_base/checks.h"
+
+namespace webrtc {
+
+class AudioBuffer;
+
+// Interface for an acoustic echo cancellation (AEC) submodule.
+class EchoControl {
+ public:
+  // Analysis (not changing) of the render signal.
+  virtual void AnalyzeRender(AudioBuffer* render) = 0;
+
+  // Analysis (not changing) of the capture signal.
+  virtual void AnalyzeCapture(AudioBuffer* capture) = 0;
+
+  // Processes the capture signal in order to remove the echo.
+  virtual void ProcessCapture(AudioBuffer* capture, bool level_change) = 0;
+
+  // As above, but also returns the linear filter output.
+  virtual void ProcessCapture(AudioBuffer* capture,
+                              AudioBuffer* linear_output,
+                              bool level_change) = 0;
+
+  struct Metrics {
+    double echo_return_loss;
+    double echo_return_loss_enhancement;
+    int delay_ms;
+  };
+
+  // Collect current metrics from the echo controller.
+  virtual Metrics GetMetrics() const = 0;
+
+  // Provides an optional external estimate of the audio buffer delay.
+  virtual void SetAudioBufferDelay(int delay_ms) = 0;
+
+  // Returns wheter the signal is altered.
+  virtual bool ActiveProcessing() const = 0;
+
+  virtual ~EchoControl() {}
+};
+
+// Interface for a factory that creates EchoControllers.
+class EchoControlFactory {
+ public:
+  virtual std::unique_ptr<EchoControl> Create(int sample_rate_hz,
+                                              int num_render_channels,
+                                              int num_capture_channels) = 0;
+
+  virtual ~EchoControlFactory() = default;
+};
+}  // namespace webrtc
+
+#endif  // API_AUDIO_ECHO_CONTROL_H_