Support for AudioContextOptions latencyHint.

third_party/WebKit/Source/modules/webaudio/AudioDestinationNode.h

Index: third_party/WebKit/Source/modules/webaudio/AudioDestinationNode.h
diff --git a/third_party/WebKit/Source/modules/webaudio/AudioDestinationNode.h b/third_party/WebKit/Source/modules/webaudio/AudioDestinationNode.h
index dc7fe45b785aa4c552a80638aed3a35d425c3ec1..ad9a8e2e69b9fabb7537c112bcb7b8ca689d22a4 100644
--- a/third_party/WebKit/Source/modules/webaudio/AudioDestinationNode.h
+++ b/third_party/WebKit/Source/modules/webaudio/AudioDestinationNode.h
@@ -39,7 +39,7 @@ class BaseAudioContext;
 
 class AudioDestinationHandler : public AudioHandler, public AudioIOCallback {
  public:
-  AudioDestinationHandler(AudioNode&, float sampleRate);
+  AudioDestinationHandler(AudioNode&);
   ~AudioDestinationHandler() override;
 
   // AudioHandler
@@ -65,6 +65,9 @@ class AudioDestinationHandler : public AudioHandler, public AudioIOCallback {
   virtual void startRendering() = 0;
   virtual void stopRendering() = 0;
 
+  virtual double sampleRate() const = 0;
+  virtual int framesPerBuffer() const = 0;

[hongchan, 2016/12/02 17:40:12]

What does this mean? Isn't it same with the 'render quantum' size? Or is it the
platform-dependent batch process size? Please make a comment.

[Andrew MacPherson, 2016/12/05 14:12:53]

This is the buffer size in frames used by the underlying audio hardware, we
should see this value changing based on the different latencyHint values. I've
now added a comment but as rtoy@ also asked about this would a different name
work better here? audioBufferSize()?

+
  protected:
   // LocalAudioInputProvider allows us to expose an AudioSourceProvider for
   // local/live audio input.  If there is local/live audio input, we call set()