chromeos: Migrate SignOut and RequestRestartForUpdate to mojo interface

ash/common/system/tray/system_tray_controller.cc

Index: ash/common/system/tray/system_tray_controller.cc
diff --git a/ash/common/system/tray/system_tray_controller.cc b/ash/common/system/tray/system_tray_controller.cc
index a097bc77a06e24c47a656699072489e489a6eebc..02fe055d6041afbb53cf3df7b182c268e2c2348e 100644
--- a/ash/common/system/tray/system_tray_controller.cc
+++ b/ash/common/system/tray/system_tray_controller.cc
@@ -103,6 +103,16 @@ void SystemTrayController::ShowProxySettings() {
     system_tray_client_->ShowProxySettings();
 }
 
+void SystemTrayController::SignOut() {
+  if (ConnectToSystemTrayClient())
+    system_tray_client_->SignOut();
+}
+
+void SystemTrayController::RequestRestartForUpdate() {
+  if (ConnectToSystemTrayClient())
+    system_tray_client_->RequestRestartForUpdate();
+}
+
 void SystemTrayController::BindRequest(mojom::SystemTrayRequest request) {
   bindings_.AddBinding(this, std::move(request));
 }