Move modules-related attributes out from Window.idl.

Source/modules/webaudio/WindowWebAudio.idl

Index: Source/modules/webaudio/WindowWebAudio.idl
diff --git a/Source/modules/webaudio/WindowWebAudio.idl b/Source/modules/webaudio/WindowWebAudio.idl
new file mode 100644
index 0000000000000000000000000000000000000000..75788e12b42a63db3912e54dbb2ecec9f95fc60b
--- /dev/null
+++ b/Source/modules/webaudio/WindowWebAudio.idl
@@ -0,0 +1,12 @@
+// Copyright (c) 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+[
+    ImplementedAs=DOMWindowWebAudio,
+] partial interface Window {
+    [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;
+};