Update the current frame count in a safe place

Source/modules/webaudio/ScriptProcessorNode.cpp

 /*
  * 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 241 matching lines @@
     if (!outputBuffer)
         return;
 
     // Avoid firing the event if the document has already gone away.
     if (context()->executionContext()) {
         // This synchronizes with process().
         MutexLocker processLocker(m_processEventLock);
 
         // Calculate a playbackTime with the buffersize which needs to be processed each time onaudioprocess is called.
         // The outputBuffer being passed to JS will be played after exhuasting previous outputBuffer by double-buffering.
-        double playbackTime = (context()->currentSampleFrame() + m_bufferSize) / static_cast<double>(context()->sampleRate());
+        double playbackTime = (context()->cachedSampleFrame() + m_bufferSize) / static_cast<double>(context()->sampleRate());
 
         // Call the JavaScript event handler which will do the audio processing.
         dispatchEvent(AudioProcessingEvent::create(inputBuffer, outputBuffer, playbackTime));
     }
 }
 
 double ScriptProcessorNode::tailTime() const
 {
     return std::numeric_limits<double>::infinity();
 }
@@ skipping 30 matching lines @@
 void ScriptProcessorNode::trace(Visitor* visitor)
 {
     visitor->trace(m_inputBuffers);
     visitor->trace(m_outputBuffers);
     AudioNode::trace(visitor);
 }
 
 } // namespace blink
 
 #endif // ENABLE(WEB_AUDIO)