Use mojo SystemTray interfaces for both mash and classic ash

ash/test/test_shell_delegate.cc

Index: ash/test/test_shell_delegate.cc
diff --git a/ash/test/test_shell_delegate.cc b/ash/test/test_shell_delegate.cc
index 3c6543c111554eaa5826b97580b89d7882e46cbd..f359bf8cfe1a1db3d9710af32dc84d98a032b085 100644
--- a/ash/test/test_shell_delegate.cc
+++ b/ash/test/test_shell_delegate.cc
@@ -112,6 +112,10 @@ TestShellDelegate::TestShellDelegate()
 
 TestShellDelegate::~TestShellDelegate() {}
 
+::shell::Connector* TestShellDelegate::GetShellConnector() const {
+  return nullptr;
+}
+
 bool TestShellDelegate::IsFirstRunAfterBoot() const {
   return false;
 }