Compute the tail time for an IIRFilter from its coefficients

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),
-        iir_(processor->Feedforward(), processor->Feedback()) {}
+  explicit IIRDSPKernel(IIRProcessor*);
 
   // AudioDSPKernel
   void Process(const float* source,
                float* dest,
                size_t frames_to_process) override;
   void Reset() override { 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 n_frequencies,
                             const float* frequency_hz,
                             float* mag_response,
                             float* phase_response);
 
   double TailTime() const override;
   double LatencyTime() const override;
 
  protected:
   IIRFilter iir_;
+
+ private:
+  double tail_time_;
 };
 
 }  // namespace blink
 
 #endif  // IIRDSPKernel_h