start/stop method for AudioBufferSourceNodes and OscillatorNodes can take no args.

Source/modules/webaudio/OscillatorNode.idl

 /*
  * Copyright (C) 2012, 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 29 matching lines @@
     const unsigned short UNSCHEDULED_STATE = 0;
     const unsigned short SCHEDULED_STATE = 1;
     const unsigned short PLAYING_STATE = 2;
     const unsigned short FINISHED_STATE = 3;
 
     readonly attribute unsigned short playbackState;
 
     readonly attribute AudioParam frequency; // in Hertz
     readonly attribute AudioParam detune; // in Cents
 
-    void start(double when);
-    void stop(double when);
+    void start(optional double when);
+    void stop(optional double when);
 
     void noteOn(double when);
     void noteOff(double when);
 
     void setPeriodicWave(PeriodicWave periodicWave);
 
     attribute EventHandler onended;
 };