Adds Mojo IDL.

third_party/WebKit/Source/core/mojo/MojoWriteMessageOptions.idl

Index: third_party/WebKit/Source/core/mojo/MojoWriteMessageOptions.idl
diff --git a/third_party/WebKit/Source/core/mojo/MojoWriteMessageOptions.idl b/third_party/WebKit/Source/core/mojo/MojoWriteMessageOptions.idl
new file mode 100644
index 0000000000000000000000000000000000000000..bf530d47d65bd721162f8a65e6a82c7ff6b2e09f
--- /dev/null
+++ b/third_party/WebKit/Source/core/mojo/MojoWriteMessageOptions.idl
@@ -0,0 +1,9 @@
+// Copyright 2017 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.
+
+dictionary MojoWriteMessageOptions {
+  BufferSource buffer;
+  sequence<MojoHandle> handles;
+  MojoWriteMessageFlags flags;

[jbroman, 2017/01/10 20:46:31]

Similarly, it would be idiomatic to have these flags expanded as separate
booleans (except that there currently are none, so you can just remove it until
there are).

[alokp, 2017/01/11 21:53:02]

Done.

+};