Add constructors for WebAudio nodes

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

Index: third_party/WebKit/Source/modules/webaudio/AudioNodeOptions.idl
diff --git a/third_party/WebKit/Source/modules/webaudio/AudioNodeOptions.idl b/third_party/WebKit/Source/modules/webaudio/AudioNodeOptions.idl
new file mode 100644
index 0000000000000000000000000000000000000000..48ca7ccf6a9c8bf62f05bf13ccc84e4cc1ff6bd1
--- /dev/null
+++ b/third_party/WebKit/Source/modules/webaudio/AudioNodeOptions.idl
@@ -0,0 +1,10 @@
+// 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/#dictionary-audionodeoptions-members
+dictionary AudioNodeOptions {
+    unsigned long channelCount;
+    ChannelCountMode channelCountMode;
+    ChannelInterpretation channelInterpretation;
+};