Implement tail processing for AudioNodes

third_party/WebKit/Source/platform/audio/DynamicsCompressorKernel.cpp

Index: third_party/WebKit/Source/platform/audio/DynamicsCompressorKernel.cpp
diff --git a/third_party/WebKit/Source/platform/audio/DynamicsCompressorKernel.cpp b/third_party/WebKit/Source/platform/audio/DynamicsCompressorKernel.cpp
index ce9bd1c0c503c1319fe13f7b614b2c921baa5324..59bbacdf70113111eca0be2f1501e44e5d74d806 100644
--- a/third_party/WebKit/Source/platform/audio/DynamicsCompressorKernel.cpp
+++ b/third_party/WebKit/Source/platform/audio/DynamicsCompressorKernel.cpp
@@ -495,4 +495,16 @@ void DynamicsCompressorKernel::Reset() {
   max_attack_compression_diff_db_ = -1;  // uninitialized state
 }
 
+double DynamicsCompressorKernel::TailTime() const {
+  // The reduction value of the compressor is computed from the gain
+  // using an exponential filter with a time constant of
+  // |kMeteringReleaseTimeConstant|.  We need to keep he compressor
+  // running for some time after the inputs go away so that the
+  // reduction value approaches 0.  This is a tradeoff between how
+  // long we keep the node alive and how close we approach the final
+  // value.  A value of 5 to 10 times the time constant is a
+  // reasonable trade-off.
+  return 5 * kMeteringReleaseTimeConstant;
+}
+
 }  // namespace blink