ScriptProcessor buffer size should be consistent with callback size

third_party/WebKit/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 325 matching lines @@
                                          float sampleRate,
                                          size_t bufferSize,
                                          unsigned numberOfInputChannels,
                                          unsigned numberOfOutputChannels)
     : AudioNode(context) {
   setHandler(ScriptProcessorHandler::create(*this, sampleRate, bufferSize,
                                             numberOfInputChannels,
                                             numberOfOutputChannels));
 }
 
-static size_t chooseBufferSize() {
+static size_t chooseBufferSize(size_t callbackBufferSize) {
   // Choose a buffer size based on the audio hardware buffer size. Arbitarily
   // make it a power of two that is 4 times greater than the hardware buffer
   // size.
   // FIXME: What is the best way to choose this?
-  size_t hardwareBufferSize = Platform::current()->audioHardwareBufferSize();
   size_t bufferSize =
-      1 << static_cast<unsigned>(log2(4 * hardwareBufferSize) + 0.5);
+      1 << static_cast<unsigned>(log2(4 * callbackBufferSize) + 0.5);
 
   if (bufferSize < 256)
     return 256;
   if (bufferSize > 16384)
     return 16384;
 
   return bufferSize;
 }
 
 ScriptProcessorNode* ScriptProcessorNode::create(
@@ skipping 61 matching lines @@
         IndexSizeError,
         "number of output channels (" + String::number(numberOfOutputChannels) +
             ") exceeds maximum (" +
             String::number(BaseAudioContext::maxNumberOfChannels()) + ").");
     return nullptr;
   }
 
   // Check for valid buffer size.
   switch (bufferSize) {
     case 0:
-      bufferSize = chooseBufferSize();
+      // Choose an appropriate size.  For an AudioContext, we need to
+      // choose an appropriate size based on the callback buffer size.
+      // For OfflineAudioContext, there's no callback buffer size, so
+      // just use the minimum valid buffer size.
+      bufferSize =
+          context.hasRealtimeConstraint()
+              ? chooseBufferSize(context.destination()->callbackBufferSize())
+              : 256;
       break;
     case 256:
     case 512:
     case 1024:
     case 2048:
     case 4096:
     case 8192:
     case 16384:
       break;
     default:
@@ skipping 28 matching lines @@
 
   // If |onaudioprocess| event handler is defined, the node should not be
   // GCed even if it is out of scope.
   if (hasEventListeners(EventTypeNames::audioprocess))
     return true;
 
   return false;
 }
 
 }  // namespace blink