Revert "chromeos: Fix shelf appearing at login screen under mash"

chrome/browser/ui/ash/session_controller_client.cc

Index: chrome/browser/ui/ash/session_controller_client.cc
diff --git a/chrome/browser/ui/ash/session_controller_client.cc b/chrome/browser/ui/ash/session_controller_client.cc
index fad60d44bd2d2948fd93239636db007fd33bbb8a..b171cf2fb7707f3345cb3223abd6af7582f7aaee 100644
--- a/chrome/browser/ui/ash/session_controller_client.cc
+++ b/chrome/browser/ui/ash/session_controller_client.cc
@@ -34,8 +34,6 @@ using user_manager::UserList;
 
 namespace {
 
-SessionControllerClient* g_instance = nullptr;
-
 uint32_t GetSessionId(const User* user) {
   const UserList logged_in_users = UserManager::Get()->GetLoggedInUsers();
   // TODO(xiyuan): Update with real session id when user session tracking
@@ -85,15 +83,9 @@ SessionControllerClient::SessionControllerClient() : binding_(this) {
   SendSessionInfoIfChanged();
   // User sessions and their order will be sent via UserSessionStateObserver
   // even for crash-n-restart.
-
-  DCHECK(!g_instance);
-  g_instance = this;
 }
 
 SessionControllerClient::~SessionControllerClient() {
-  DCHECK_EQ(this, g_instance);
-  g_instance = nullptr;
-
   SessionManager::Get()->RemoveObserver(this);
   UserManager::Get()->RemoveSessionStateObserver(this);
 }
@@ -233,11 +225,6 @@ void SessionControllerClient::DoCycleActiveUser(bool next_user) {
   DoSwitchActiveUser(account_id);
 }
 
-// static
-void SessionControllerClient::FlushForTesting() {
-  g_instance->session_controller_.FlushForTesting();
-}
-
 void SessionControllerClient::OnSessionStateChanged() {
   SendSessionInfoIfChanged();
 }