Support both prefixed and unprefixed AudioContext and OfflineAudioContext.

Source/core/frame/Window.idl

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2011 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
@@ skipping 198 matching lines @@
     attribute IDBFactoryConstructor webkitIDBFactory;
     attribute IDBIndexConstructor webkitIDBIndex;
     attribute IDBKeyRangeConstructor webkitIDBKeyRange;
     attribute IDBObjectStoreConstructor webkitIDBObjectStore;
     attribute IDBRequestConstructor webkitIDBRequest;
     attribute IDBTransactionConstructor webkitIDBTransaction;
 
     // Constructors whose name does not match the interface name.
     // FIXME: Remove these once [ImplementedAs] is used and once constructor names match interface names.
     [RuntimeEnabled=MediaStream] attribute MediaStreamConstructor webkitMediaStream;
+    // Support both prefixed and unprefixed WebAudio
     [Conditional=WEB_AUDIO, RuntimeEnabled=WebAudio] attribute AudioContextConstructor AudioContext;
     [Conditional=WEB_AUDIO, RuntimeEnabled=WebAudio] attribute OfflineAudioContextConstructor OfflineAudioContext;
+    [Conditional=WEB_AUDIO, RuntimeEnabled=WebAudio] attribute AudioContextConstructor webkitAudioContext;
+    [Conditional=WEB_AUDIO, RuntimeEnabled=WebAudio] attribute OfflineAudioContextConstructor webkitOfflineAudioContext;
     [RuntimeEnabled=PeerConnection] attribute RTCPeerConnectionConstructor webkitRTCPeerConnection;
     [RuntimeEnabled=ScriptedSpeech] attribute SpeechGrammarConstructor webkitSpeechGrammar;
     [RuntimeEnabled=ScriptedSpeech] attribute SpeechGrammarListConstructor webkitSpeechGrammarList;
     [RuntimeEnabled=ScriptedSpeech] attribute SpeechRecognitionConstructor webkitSpeechRecognition;
     [RuntimeEnabled=ScriptedSpeech] attribute SpeechRecognitionErrorConstructor webkitSpeechRecognitionError;
     [RuntimeEnabled=ScriptedSpeech] attribute SpeechRecognitionEventConstructor webkitSpeechRecognitionEvent;
 
     // window.toString() requires special handling in V8
     [DoNotCheckSignature, DoNotCheckSecurity, Custom, NotEnumerable] DOMString toString();
 
     [NotEnumerable] getter Window (unsigned long index);
     [Custom, NotEnumerable] getter Window (DOMString name);
 };
 
 Window implements GlobalEventHandlers;
 Window implements ImageBitmapFactories;
 Window implements WindowBase64;
 Window implements WindowEventHandlers;
 Window implements WindowTimers;