Convert //mash to define service names in mojom

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 5513d3d13f38cb1dd56fdf6f056cda845a7ccdb7..7ce7e904e3e45a634c1391b28c9a3787d49f3778 100644
--- a/ash/common/system/tray/system_tray_controller.cc
+++ b/ash/common/system/tray/system_tray_controller.cc
@@ -8,6 +8,7 @@
 #include "ash/common/wm_shell.h"
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "content/public/common/service_names.mojom.h"
 #include "services/service_manager/public/cpp/connector.h"
 
 namespace ash {
@@ -128,7 +129,8 @@ bool SystemTrayController::ConnectToSystemTrayClient() {
     return true;
 
   // Connect (or reconnect) to the interface.
-  connector_->ConnectToInterface("content_browser", &system_tray_client_);
+  connector_->ConnectToInterface(content::mojom::kBrowserServiceName,
+                                 &system_tray_client_);
 
   // Handle chrome crashes by forcing a reconnect on the next request.
   system_tray_client_.set_connection_error_handler(base::Bind(