Supporting a playbackTime attribute on AudioprocessingEvent.

Source/modules/webaudio/AudioContext.idl

 /*
  * Copyright (C) 2010, Google Inc. All rights reserved.
  * Copyright (C) 2011 Apple 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
@@ skipping 18 matching lines @@
     Constructor,
     Constructor(unsigned long numberOfChannels, unsigned long numberOfFrames, float sampleRate),
     ConstructorCallWith=Document,
     NoInterfaceObject,
     RaisesException=Constructor,
 ] interface AudioContext : EventTarget {
     // All rendered audio ultimately connects to destination, which represents the audio hardware.
     readonly attribute AudioDestinationNode destination;
 
     // All scheduled times are relative to this time in seconds.
-    readonly attribute float currentTime;
+    readonly attribute double currentTime;
 
     // All AudioNodes in the context run at this sample-rate (sample-frames per second).
     readonly attribute float sampleRate;
 
     // All panning is relative to this listener.
     readonly attribute AudioListener listener;
 
     // Number of AudioBufferSourceNodes that are currently playing.
     readonly attribute unsigned long activeSourceCount;
 
@@ skipping 32 matching lines @@
     // void prepareOfflineBufferRendering(unsigned long numberOfChannels, unsigned long numberOfFrames, float sampleRate);
     attribute EventHandler oncomplete;
     void startRendering();
 
     [MeasureAs=LegacyWebAudio, ImplementedAs=createGain] GainNode createGainNode();
     [MeasureAs=LegacyWebAudio, ImplementedAs=createDelay, RaisesException] DelayNode createDelayNode(optional double maxDelayTime);
 
     [MeasureAs=LegacyWebAudio, ImplementedAs=createScriptProcessor, RaisesException] ScriptProcessorNode createJavaScriptNode(unsigned long bufferSize, optional unsigned long numberOfInputChannels, optional unsigned long numberOfOutputChannels);
 
 };