Avoid slow AudioParam automation path when possible

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

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 49 matching lines @@
     // returns the last parameter value calculated for "values" or the defaultValue if none were
     // calculated.  controlRate is the rate (number per second) at which parameter values will be
     // calculated.  It should equal sampleRate for sample-accurate parameter changes, and otherwise
     // will usually match the render quantum size such that the parameter value changes once per
     // render quantum.
     float valuesForFrameRange(size_t startFrame, size_t endFrame, float defaultValue, float* values, unsigned numberOfValues, double sampleRate, double controlRate, float minValue, float maxValue);
 
     // Returns true if this AudioParam has any events on it.
     bool hasValues() const;
 
+    float smoothedValue() { return m_smoothedValue; }
+    void setSmoothedValue(float v) { m_smoothedValue = v; }
 private:
     class ParamEvent {
     public:
         enum Type {
             SetValue,
             LinearRampToValue,
             ExponentialRampToValue,
             SetTarget,
             SetValueCurve,
             LastType
@@ skipping 34 matching lines @@
     };
 
     void insertEvent(const ParamEvent&, ExceptionState&);
     float valuesForFrameRangeImpl(size_t startFrame, size_t endFrame, float defaultValue, float* values, unsigned numberOfValues, double sampleRate, double controlRate);
 
     // Produce a nice string describing the event in human-readable form.
     String eventToString(const ParamEvent&);
     Vector<ParamEvent> m_events;
 
     mutable Mutex m_eventsLock;
+
+    // Smoothing (de-zippering)
+    float m_smoothedValue;
 };
 
 } // namespace blink
 
 #endif // AudioParamTimeline_h