Add constructors for WebAudio events

third_party/WebKit/Source/modules/webaudio/OfflineAudioCompletionEventInit.idl

Index: third_party/WebKit/Source/modules/webaudio/OfflineAudioCompletionEventInit.idl
diff --git a/third_party/WebKit/Source/modules/webaudio/OfflineAudioCompletionEventInit.idl b/third_party/WebKit/Source/modules/webaudio/OfflineAudioCompletionEventInit.idl
new file mode 100644
index 0000000000000000000000000000000000000000..c70ba7cfc8c3cc2d7c321a2dd4493aee587b8dbf
--- /dev/null
+++ b/third_party/WebKit/Source/modules/webaudio/OfflineAudioCompletionEventInit.idl
@@ -0,0 +1,8 @@
+// Copyright 2016 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.
+
+// See https://webaudio.github.io/web-audio-api/#offlineaudiocompletioneventinit
+dictionary OfflineAudioCompletionEventInit : EventInit {
+    required AudioBuffer renderedBuffer;
+};