Use mojo SystemTray interfaces for both mash and classic ash

ash/shell_init_params.h

Index: ash/shell_init_params.h
diff --git a/ash/shell_init_params.h b/ash/shell_init_params.h
index 8cff2f1d9567887f8b82090d0f70789a3c9d61e4..5307dcd82598bfd200e59553cba5865d74134f71 100644
--- a/ash/shell_init_params.h
+++ b/ash/shell_init_params.h
@@ -11,6 +11,10 @@ namespace base {
 class SequencedWorkerPool;
 }
 
+namespace shell {
+class Connector;
+}
+
 namespace ui {
 class ContextFactory;
 }
@@ -23,6 +27,7 @@ struct ASH_EXPORT ShellInitParams {
   ShellDelegate* delegate = nullptr;
   ui::ContextFactory* context_factory = nullptr;
   base::SequencedWorkerPool* blocking_pool = nullptr;
+  ::shell::Connector* connector = nullptr;
 };
 
 }  // namespace ash