Revert regression in AudioBufferSourceNode.start() with no buffer

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 05d2db905ccb52f95ad44f7402bd349393a9c07e..d8efe5b2f13c529c4a309c85672a71039b059c00 100644
--- a/Source/modules/webaudio/AudioBufferSourceNode.h
+++ b/Source/modules/webaudio/AudioBufferSourceNode.h
@@ -60,7 +60,7 @@ public:
     unsigned numberOfChannels();
 
     // Play-state
-    void start(ExceptionState&);
+    void start(ExceptionState& exceptionState) { start(0, exceptionState); }
     void start(double when, ExceptionState&);
     void start(double when, double grainOffset, ExceptionState&);
     void start(double when, double grainOffset, double grainDuration, ExceptionState&);
@@ -95,8 +95,6 @@ public:
 private:
     AudioBufferSourceNode(AudioContext*, float sampleRate);
 
-    void startPlaying(bool isGrain, double when, double grainOffset, double grainDuration, ExceptionState&);
-
     // Returns true on success.
     bool renderFromBuffer(AudioBus*, unsigned destinationFrameOffset, size_t numberOfFrames);