Access current frame counter carefully and remove m_cachedSampleFrame.

Source/modules/webaudio/AudioDestinationNode.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 30 matching lines @@
     AudioDestinationHandler(AudioNode&, float sampleRate);
     virtual ~AudioDestinationHandler();
 
     // AudioHandler
     virtual void process(size_t) override final { } // we're pulled by hardware so this is never called
 
     // The audio hardware calls render() to get the next render quantum of audio into destinationBus.
     // It will optionally give us local/live audio input in sourceBus (if it's not 0).
     virtual void render(AudioBus* sourceBus, AudioBus* destinationBus, size_t numberOfFrames) override final;
 
-    size_t currentSampleFrame() const { return m_currentSampleFrame; }
+    size_t currentSampleFrame() const { return acquireLoad(&m_currentSampleFrame); }
     double currentTime() const { return currentSampleFrame() / static_cast<double>(sampleRate()); }
 
     virtual unsigned long maxChannelCount() const { return 0; }
 
     virtual void startRendering() = 0;
     virtual void stopRendering() = 0;
 
 protected:
     // LocalAudioInputProvider allows us to expose an AudioSourceProvider for local/live audio input.
     // If there is local/live audio input, we call set() with the audio input data every render quantum.
@@ skipping 36 matching lines @@
 
     unsigned long maxChannelCount() const;
 
 protected:
     AudioDestinationNode(AudioContext&);
 };
 
 } // namespace blink
 
 #endif // AudioDestinationNode_h