Signal exceptions if start/stop is called out-of-order or too many times.

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 e203419425b843b5f667c0c124a65319edc22b36..0b5962a39bd7a81c748766e27b65d80560a44625 100644
--- a/Source/modules/webaudio/OscillatorNode.idl
+++ b/Source/modules/webaudio/OscillatorNode.idl
@@ -47,11 +47,11 @@
     readonly attribute AudioParam frequency; // in Hertz
     readonly attribute AudioParam detune; // in Cents
 
-    void start(optional double when);
-    void stop(optional double when);
+    [RaisesException] void start(optional double when);
+    [RaisesException] void stop(optional double when);
 
-    void noteOn(double when);
-    void noteOff(double when);
+    [RaisesException, ImplementedAs=start] void noteOn(double when);
+    [RaisesException, ImplementedAs=stop] void noteOff(double when);
 
     void setPeriodicWave(PeriodicWave periodicWave);