Have bindings layer assume and insist that all interface types are GCed.

third_party/WebKit/Source/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:
  *
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  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
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  *     its contributors may be used to endorse or promote products derived
  *     from this software without specific prior written permission.
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  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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 [
-    GarbageCollected,
 ] interface AudioParam {
     attribute float value;
     readonly attribute float defaultValue;
 
     // Parameter automation.
     [RaisesException, MeasureAs=AudioParamSetValueAtTime] AudioParam setValueAtTime(float value, double time);
     [RaisesException, MeasureAs=AudioParamLinearRampToValueAtTime] AudioParam linearRampToValueAtTime(float value, double time);
     [RaisesException, MeasureAs=AudioParamExponentialRampToValueAtTime] AudioParam exponentialRampToValueAtTime(float value, double time);
 
     // Exponentially approach the target with a rate having the given time constant.
     [RaisesException, MeasureAs=AudioParamSetTargetAtTime] AudioParam 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.
     [RaisesException, MeasureAs=AudioParamSetValueCurveAtTime] AudioParam setValueCurveAtTime(Float32Array values, double time, double duration);
 
     // Cancels all scheduled parameter changes with times greater than or equal to startTime.
     [RaisesException, MeasureAs=AudioParamCancelScheduledValues] AudioParam cancelScheduledValues(double startTime);
 
 };