Use mojo SystemTray interfaces for both mash and classic ash

ash/common/mojo_interface_factory.cc

Index: ash/common/mojo_interface_factory.cc
diff --git a/ash/common/mojo_interface_factory.cc b/ash/common/mojo_interface_factory.cc
new file mode 100644
index 0000000000000000000000000000000000000000..498ff264f9285f9544fe556fbd00727dc5b8c96c
--- /dev/null
+++ b/ash/common/mojo_interface_factory.cc
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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.
+
+#include "ash/common/mojo_interface_factory.h"
+
+#include "ash/common/system/tray/system_tray_controller.h"
+#include "ash/common/wm_shell.h"
+#include "base/bind.h"
+#include "services/shell/public/cpp/interface_registry.h"
+
+namespace ash {
+
+namespace {
+
+void BindSystemTrayRequestOnMainThread(mojom::SystemTrayRequest request) {
+  WmShell::Get()->system_tray_controller()->BindRequest(std::move(request));
+}
+
+}  // namespace
+
+namespace mojo_interface_factory {
+
+void RegisterInterfaces(
+    shell::InterfaceRegistry* registry,
+    scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner) {
+  registry->AddInterface(base::Bind(&BindSystemTrayRequestOnMainThread),
+                         main_thread_task_runner);
+}
+
+}  // namespace mojo_interface_factory
+
+}  // namespace ash