chromeos: Refactor system tray ShowNetworkSettingsForGuid for mash

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 d5dd3f798dcf5b851f0453f9ddc50c2a7f206a15..f91ecfdb045989adb0d1022f06ebdfe3a7193987 100644
--- a/ash/common/system/tray/system_tray_controller.cc
+++ b/ash/common/system/tray/system_tray_controller.cc
@@ -77,6 +77,11 @@ void SystemTrayController::ShowPublicAccountInfo() {
     system_tray_client_->ShowPublicAccountInfo();
 }
 
+void SystemTrayController::ShowNetworkSettings(const std::string& network_id) {
+  if (ConnectToSystemTrayClient())
+    system_tray_client_->ShowNetworkSettings(network_id);
+}
+
 void SystemTrayController::ShowProxySettings() {
   if (ConnectToSystemTrayClient())
     system_tray_client_->ShowProxySettings();