Support for AudioContextOptions latencyHint.

third_party/WebKit/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 21 matching lines @@
 #include "platform/audio/AudioIOCallback.h"
 #include "platform/audio/AudioSourceProvider.h"
 
 namespace blink {
 
 class AudioBus;
 class BaseAudioContext;
 
 class AudioDestinationHandler : public AudioHandler, public AudioIOCallback {
  public:
-  AudioDestinationHandler(AudioNode&, float sampleRate);
+  AudioDestinationHandler(AudioNode&);
   ~AudioDestinationHandler() override;
 
   // AudioHandler
   void process(size_t) 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).
   void render(AudioBus* sourceBus,
               AudioBus* destinationBus,
               size_t numberOfFrames) final;
 
   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;
 
+  virtual double sampleRate() const = 0;
+
+  // Returns the audio buffer size in frames used by the underlying audio
+  // hardware.

[Raymond Toy, 2016/12/08 17:14:38]

This isn't the size of the underlying audio hardware is it? Isn't it the buffer
size for the AudioContext, which is related to the audio hardware size, but not
necessary equal to it.

[Andrew MacPherson, 2016/12/09 12:34:14]

Makes sense, I've updated it now.

+  virtual int framesPerBuffer() const = 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.
   class LocalAudioInputProvider final : public AudioSourceProvider {
    public:
     LocalAudioInputProvider()
         : m_sourceBus(AudioBus::create(
               2,
               AudioUtilities::kRenderQuantumFrames))  // FIXME: handle
@@ skipping 34 matching lines @@
 
   unsigned long maxChannelCount() const;
 
  protected:
   AudioDestinationNode(BaseAudioContext&);
 };
 
 }  // namespace blink
 
 #endif  // AudioDestinationNode_h