Adds Mojo IDL.

third_party/WebKit/Source/core/mojo/MojoHandleWatcher.h

Index: third_party/WebKit/Source/core/mojo/MojoHandleWatcher.h
diff --git a/third_party/WebKit/Source/core/mojo/MojoHandleWatcher.h b/third_party/WebKit/Source/core/mojo/MojoHandleWatcher.h
new file mode 100644
index 0000000000000000000000000000000000000000..ba2bccf5f59b0a98b44ab2c25158a69e799f869e
--- /dev/null
+++ b/third_party/WebKit/Source/core/mojo/MojoHandleWatcher.h
@@ -0,0 +1,42 @@
+// 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.
+
+#ifndef MojoHandleWatcher_h
+#define MojoHandleWatcher_h
+
+#include "mojo/public/c/system/core.h"
+#include "wtf/Functional.h"
+
+namespace blink {
+
+class WebTaskRunner;
+
+class MojoHandleWatcher {
+ public:
+  using ReadyCallback = WTF::Function<void(MojoResult)>;
+
+  MojoHandleWatcher(WebTaskRunner*);
+  ~MojoHandleWatcher();
+
+  MojoResult start(MojoHandle,
+                   MojoHandleSignals,
+                   std::unique_ptr<ReadyCallback>);
+  void cancel();
+
+ private:
+  class RunReadyCallbackTask;
+  static void onHandleReady(uintptr_t,
+                            MojoResult,
+                            MojoHandleSignalsState,
+                            MojoWatchNotificationFlags);
+  void runReadyCallback(MojoResult);
+
+  WebTaskRunner* m_taskRunner;

[Ken Rockot(use gerrit already), 2016/10/18 15:47:10]

nit: WebTaskRunner* const to guarantee m_taskRunner never changes. Otherwise
onHandleReady's thread-safety is unclear

[alokp, 2016/10/18 16:48:37]

Done.

+  MojoHandle m_handle;
+  std::unique_ptr<ReadyCallback> m_callback;
+};
+
+}  // namespace blink
+
+#endif  // MojoHandleWatcher_h