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

Source/modules/webaudio/AudioBufferSourceNode.h

Index: Source/modules/webaudio/AudioBufferSourceNode.h
diff --git a/Source/modules/webaudio/AudioBufferSourceNode.h b/Source/modules/webaudio/AudioBufferSourceNode.h
index 99e7c0778bafd620bf52520ed9c046e23eea1ced..015e2e0fdda68f027dbc02cb32e342d694631473 100644
--- a/Source/modules/webaudio/AudioBufferSourceNode.h
+++ b/Source/modules/webaudio/AudioBufferSourceNode.h
@@ -61,9 +61,10 @@ public:
     unsigned numberOfChannels();
 
     // Play-state
-    void start(double when = 0);
-    void start(double when, double grainOffset);
-    void start(double when, double grainOffset, double grainDuration);
+    void start(ExceptionState&);
+    void start(double when, ExceptionState&);
+    void start(double when, double grainOffset, ExceptionState&);
+    void start(double when, double grainOffset, double grainDuration, ExceptionState&);
 
     void noteGrainOn(double when, double grainOffset, double grainDuration);
 
@@ -96,6 +97,7 @@ private:
     AudioBufferSourceNode(AudioContext*, float sampleRate);
 
     void startPlaying(bool isGrain, double when, double grainOffset, double grainDuration);

[Ken Russell (switch to Gerrit), 2013/10/31 21:58:22]

Could you please delete this overload and just fold its body into the version
taking ExceptionState& as the last argument?

[Raymond Toy (Google), 2013/10/31 22:12:45]

It's needed by noteGrainOn, which doesn't pass in an exception.  I can make
noteGrainOn raise exceptions and get rid of the extra startPlaying.

[Ken Russell (switch to Gerrit), 2013/10/31 22:14:25]

I think that would be better.

[Raymond Toy (Google), 2013/10/31 22:30:54]

Done.

+    void startPlaying(bool isGrain, double when, double grainOffset, double grainDuration, ExceptionState&);
 
     // Returns true on success.
     bool renderFromBuffer(AudioBus*, unsigned destinationFrameOffset, size_t numberOfFrames);