Update IDL to 1847

modules/webaudio/AudioParam.idl

 /*
  * Copyright (C) 2010 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 24 matching lines @@
     readonly attribute float defaultValue;
 
     readonly attribute DOMString name;
 
     // FIXME: Could define units constants here (seconds, decibels, cents, etc.)...
     readonly attribute unsigned short units;
 
     // Parameter automation.
     void setValueAtTime(float value, double time);
     void linearRampToValueAtTime(float value, double time);
-    void exponentialRampToValueAtTime(float value, double time);
+    [RaisesException] void exponentialRampToValueAtTime(float value, double time);
 
     // Exponentially approach the target with a rate having the given time constant.
     void setTargetAtTime(float target, double time, double timeConstant);
 
     // Sets an array of arbitrary parameter values starting at time for the given duration.
     // The number of values will be scaled to fit into the desired duration.
     void setValueCurveAtTime(Float32Array values, double time, double duration);
 
     // Cancels all scheduled parameter changes with times greater than or equal to startTime.
     void cancelScheduledValues(double startTime);
 
     [MeasureAs=LegacyWebAudio, ImplementedAs=setTargetAtTime] void setTargetValueAtTime(float targetValue, double time, double timeConstant);
 
 };