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

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 77cea02d66913dbc673575b267e17c65a218189f..99e7c0778bafd620bf52520ed9c046e23eea1ced 100644
--- a/Source/modules/webaudio/AudioBufferSourceNode.h
+++ b/Source/modules/webaudio/AudioBufferSourceNode.h
@@ -61,8 +61,9 @@ public:
     unsigned numberOfChannels();
 
     // Play-state
-    void startGrain(double when, double grainOffset);
-    void startGrain(double when, double grainOffset, double grainDuration);
+    void start(double when = 0);
+    void start(double when, double grainOffset);
+    void start(double when, double grainOffset, double grainDuration);
 
     void noteGrainOn(double when, double grainOffset, double grainDuration);
 
@@ -94,6 +95,8 @@ public:
 private:
     AudioBufferSourceNode(AudioContext*, float sampleRate);
 
+    void startPlaying(bool isGrain, double when, double grainOffset, double grainDuration);
+
     // Returns true on success.
     bool renderFromBuffer(AudioBus*, unsigned destinationFrameOffset, size_t numberOfFrames);