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
new file mode 100644
index 0000000000000000000000000000000000000000..9209188a93195684d5e737a6eb2652656a2f42cf
--- /dev/null
+++ b/ash/common/mojo_interface_factory.h
@@ -0,0 +1,37 @@
+// 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 {
+
+class ASH_EXPORT MojoInterfaceFactory {

[James Cook, 2016/09/30 21:18:26]

I could also add namespace mojo_interface_factory and have a bare function
ash::mojo_interface_factory::RegisterInterfaces, but I went with this because
it's similar to ChromeInterfaceFactory.

I don't want to have a bare function in the ash namespace because I find that
hard to read at the call site.

[msw, 2016/09/30 23:26:48]

This seems fine to me.

+ public:
+  // 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).
+  static void RegisterInterfaces(
+      shell::InterfaceRegistry* registry,
+      scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner);
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(MojoInterfaceFactory);
+};
+
+}  // namespace ash
+
+#endif  // ASH_COMMON_MOJO_INTERFACE_FACTORY_H_