Implement IIRFilter node for WebAudio.

third_party/WebKit/Source/modules/webaudio/IIRDSPKernel.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef IIRDSPKernel_h
+#define IIRDSPKernel_h
+
+#include "modules/webaudio/IIRProcessor.h"
+#include "platform/audio/AudioDSPKernel.h"
+#include "platform/audio/IIRFilter.h"
+
+namespace blink {
+
+class IIRProcessor;
+
+class IIRDSPKernel final : public AudioDSPKernel {
+public:
+    explicit IIRDSPKernel(IIRProcessor* processor)
+        : AudioDSPKernel(processor)
+        , m_iir(processor->feedforward(), processor->feedback())
+    {
+    }
+
+    // AudioDSPKernel
+    void process(const float* source, float* dest, size_t framesToProcess) override;
+    void reset() override { m_iir.reset(); }
+
+    // Get the magnitude and phase response of the filter at the given
+    // set of frequencies (in Hz). The phase response is in radians.
+    void getFrequencyResponse(int nFrequencies, const float* frequencyHz, float* magResponse, float* phaseResponse);
+
+    double tailTime() const override;
+    double latencyTime() const override;
+
+protected:
+    IIRFilter m_iir;
+};
+
+} // namespace blink
+
+#endif // IIRDSPKernel_h