Compute tail time from Biquad coefficients

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

Index: third_party/WebKit/Source/modules/webaudio/BiquadDSPKernel.h
diff --git a/third_party/WebKit/Source/modules/webaudio/BiquadDSPKernel.h b/third_party/WebKit/Source/modules/webaudio/BiquadDSPKernel.h
index efeb3eb027572dabb1bc7e0171297ad860dbce1a..915bf2e5677eae34e62f196dc435f7c77c519c64 100644
--- a/third_party/WebKit/Source/modules/webaudio/BiquadDSPKernel.h
+++ b/third_party/WebKit/Source/modules/webaudio/BiquadDSPKernel.h
@@ -40,7 +40,8 @@ class BiquadProcessor;
 class BiquadDSPKernel final : public AudioDSPKernel {
  public:
   explicit BiquadDSPKernel(BiquadProcessor* processor)
-      : AudioDSPKernel(processor) {}
+      : AudioDSPKernel(processor),
+        tail_time_(std::numeric_limits<double>::infinity()) {}
 
   // AudioDSPKernel
   void Process(const float* source,
@@ -75,8 +76,15 @@ class BiquadDSPKernel final : public AudioDSPKernel {
                           const float* detune);
 
  private:
+  // Compute the tail time using the BiquadFilter coefficients at
+  // index |coef_index|.
+  void UpdateTailTime(int coef_index);
+
   // Synchronize process() with getting and setting the filter coefficients.
   mutable Mutex process_lock_;
+
+  // The current tail time for biquad filter.
+  double tail_time_;
 };
 
 }  // namespace blink