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..a50a40cc76d679db4b45b4f587c4b965340ff8d6
--- /dev/null
+++ b/ash/common/mojo_interface_factory.cc
@@ -0,0 +1,30 @@
+// 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
+
+// static
+void MojoInterfaceFactory::RegisterInterfaces(
+    shell::InterfaceRegistry* registry,
+    scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner) {
+  registry->AddInterface(base::Bind(&BindSystemTrayRequestOnMainThread),
+                         main_thread_task_runner);
+}
+
+}  // namespace ash