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

Source/modules/webaudio/OscillatorNode.idl

Index: Source/modules/webaudio/OscillatorNode.idl
diff --git a/Source/modules/webaudio/OscillatorNode.idl b/Source/modules/webaudio/OscillatorNode.idl
index 949eac60c32695668c17a31b39d59360174a820f..e203419425b843b5f667c0c124a65319edc22b36 100644
--- a/Source/modules/webaudio/OscillatorNode.idl
+++ b/Source/modules/webaudio/OscillatorNode.idl
@@ -47,8 +47,8 @@
     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);