Adds Mojo IDL.

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

Index: third_party/WebKit/Source/core/mojo/MojoHandle.idl
diff --git a/third_party/WebKit/Source/core/mojo/MojoHandle.idl b/third_party/WebKit/Source/core/mojo/MojoHandle.idl
new file mode 100644
index 0000000000000000000000000000000000000000..ea64ac623e5d27a35f24ac305f174d6a58bf574c
--- /dev/null
+++ b/third_party/WebKit/Source/core/mojo/MojoHandle.idl
@@ -0,0 +1,12 @@
+// 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.
+
+callback MojoWatchCallback = void (MojoResult result);
+
+interface MojoHandle {
+    void close();
+    [CallWith=ScriptState] MojoWatcher watch(MojoWatchOptions options, MojoWatchCallback callback);
+    MojoResult writeMessage(MojoWriteMessageOptions options);

[yzshen1, 2017/01/12 23:38:35]

Does it make sense to do:
- introduce subclass MojoMessagePipeHandle and move these methods there;
- introduce down-cast methods in MojoHandle such as "asMessagePipe".

[alokp, 2017/01/13 01:07:56]

Good Idea. I will prefer to do it in a followup patch though to make it easier
to port over current usage without significant changes.

+    MojoReadMessageResult readMessage(optional MojoReadMessageOptions options);
+};