Change the default panning mode from HRTF to equal-power

Source/modules/webaudio/PannerNode.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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 19 matching lines @@
 enum DistanceModelType {
     "linear",
     "inverse",
     "exponential"
 };
 
 [
     NoInterfaceObject,
     Conditional=WEB_AUDIO
 ] interface PannerNode : AudioNode {
-    // Default model for stereo is HRTF
+    // Default model for stereo is equalpower.
     attribute PanningModelType panningModel;
 
     // Uses a 3D cartesian coordinate system
     void setPosition(float x, float y, float z);
     void setOrientation(float x, float y, float z);
     void setVelocity(float x, float y, float z);
 
     // Distance model
     attribute DistanceModelType distanceModel;
 
     attribute double refDistance;
     attribute double maxDistance;
     attribute double rolloffFactor;
 
     // Directional sound cone
     attribute double coneInnerAngle;
     attribute double coneOuterAngle;
     attribute double coneOuterGain;
-};
+};