Move many calls of lazyInitialize() from AudioContext to AudioNode.

Source/modules/webaudio/AudioContext.h

 /*
  * Copyright (C) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 67 matching lines @@
 public:
     // Create an AudioContext for rendering to the audio hardware.
     static PassRefPtr<AudioContext> create(Document&, ExceptionState&);
 
     // Deprecated: create an AudioContext for offline (non-realtime) rendering.
     static PassRefPtr<AudioContext> create(Document&, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate, ExceptionState&);
 
     virtual ~AudioContext();
 
     bool isInitialized() const;
+    // This is called on constructor of AudioNode when the first node of context is created except destination node.

[Raymond Toy, 2014/04/02 17:11:32]

I think this comment is slightly wrong because the destination node is an
AudioNode.  When the destination node is created the AudioNode constructor is
called, but since m_destinationNode isn't set yet, nothing happens.

Maybe the following is better?
// The constructor of an AudioNode must call this to initialize the context.

[KhNo, 2014/04/03 13:21:02]

Done.

+    void lazyInitialize();
 
     bool isOfflineContext() { return m_isOfflineContext; }
 
     // Document notification
     virtual void stop() OVERRIDE FINAL;
     virtual bool hasPendingActivity() const OVERRIDE;
 
     AudioDestinationNode* destination() { return m_destinationNode.get(); }
     size_t currentSampleFrame() const { return m_destinationNode->currentSampleFrame(); }
     double currentTime() const { return m_destinationNode->currentTime(); }
@@ skipping 140 matching lines @@
 
 protected:
     explicit AudioContext(Document*);
     AudioContext(Document*, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate);
 
     static bool isSampleRateRangeGood(float sampleRate);
 
 private:
     void constructCommon();
 
-    void lazyInitialize();
     void uninitialize();
 
     // ExecutionContext calls stop twice.
     // We'd like to schedule only one stop action for them.
     bool m_isStopScheduled;
     static void stopDispatch(void* userData);
     bool m_isCleared;
     void clear();
 
     void scheduleNodeDeletion();
@@ skipping 68 matching lines @@
     // It is somewhat arbitrary and could be increased if necessary.
     enum { MaxNumberOfChannels = 32 };
 
     // Number of AudioBufferSourceNodes that are active (playing).
     int m_activeSourceCount;
 };
 
 } // WebCore
 
 #endif // AudioContext_h