Use mojo SystemTray interfaces for both mash and classic ash

ash/common/mojo_interface_factory.h

Index: ash/common/mojo_interface_factory.h
diff --git a/ash/common/mojo_interface_factory.h b/ash/common/mojo_interface_factory.h
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+++ b/ash/common/mojo_interface_factory.h
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+// 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 ASH_COMMON_MOJO_INTERFACE_FACTORY_H_
+#define ASH_COMMON_MOJO_INTERFACE_FACTORY_H_
+
+#include "ash/ash_export.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
+
+namespace shell {
+class InterfaceRegistry;
+}
+
+namespace ash {
+
+namespace mojo_interface_factory {
+
+// Registers all mojo services provided by ash. May be called on IO thread
+// (when running ash in-process in chrome) or on the main thread (when running
+// in mash).
+ASH_EXPORT void RegisterInterfaces(
+    shell::InterfaceRegistry* registry,
+    scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner);
+
+}  // namespace mojo_interface_factory
+
+}  // namespace ash
+
+#endif  // ASH_COMMON_MOJO_INTERFACE_FACTORY_H_