Tray elements behave appropriately on the multiple signin screen (more like lock screen)

ash/test/test_session_state_delegate.cc

Index: ash/test/test_session_state_delegate.cc
diff --git a/ash/test/test_session_state_delegate.cc b/ash/test/test_session_state_delegate.cc
index 8831b58d6b1e7393df2fb6795cd7fc40828359f7..5315f15fa1a0a328e7210ad4d7b6e4ed29bcb620 100644
--- a/ash/test/test_session_state_delegate.cc
+++ b/ash/test/test_session_state_delegate.cc
@@ -234,5 +234,8 @@ void TestSessionStateDelegate::RemoveSessionStateObserver(
     SessionStateObserver* observer) {
 }
 
+void TestSessionStateDelegate::HideMultipleSigninScreen() {
+}
+
 }  // namespace test
 }  // namespace ash