Support both prefixed and unprefixed AudioContext and OfflineAudioContext.

Source/core/frame/Window.idl

Index: Source/core/frame/Window.idl
diff --git a/Source/core/frame/Window.idl b/Source/core/frame/Window.idl
index ebecb7fc5baff0aedf158f593b9eb5c88d903d4d..e8eea0301663ea2fa06cfd3cf299ebd3457d3463 100644
--- a/Source/core/frame/Window.idl
+++ b/Source/core/frame/Window.idl
@@ -216,8 +216,11 @@
     // 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;