user_manager component: Add UserManagerBase class.

components/session_manager/core/session_manager.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/session_manager/core/session_manager.h"
 
 #include "base/logging.h"
 
+#if defined(OS_CHROMEOS)
+#include "base/command_line.h"
+#include "base/sys_info.h"
+#include "chromeos/chromeos_switches.h"
+#endif
+
 namespace session_manager {
 
+// static
+SessionManager* SessionManager::instance = NULL;
+
 SessionManager::SessionManager() : session_state_(SESSION_STATE_UNKNOWN) {
+  DCHECK(!SessionManager::Get());
+  SessionManager::SetInstance(this);
 }
 
 SessionManager::~SessionManager() {
+  SessionManager::SetInstance(NULL);
+}
+
+// static
+SessionManager* SessionManager::Get() {
+  return SessionManager::instance;
 }
 
 void SessionManager::SetSessionState(SessionState state) {
   VLOG(1) << "Changing session state to: " << state;
 
   if (session_state_ != state) {
     // TODO(nkostylev): Notify observers about the state change.
     // TODO(nkostylev): Add code to process session state change and probably
     // replace delegate_ if needed.
     session_state_ = state;
   }
 }
 
 void SessionManager::Initialize(SessionManagerDelegate* delegate) {
   DCHECK(delegate);
   delegate_.reset(delegate);
   delegate_->SetSessionManager(this);
 }
 
+// static
+void SessionManager::SetInstance(SessionManager* session_manager) {
+  SessionManager::instance = session_manager;
+}
+
 void SessionManager::Start() {
   delegate_->Start();
 }
 
+// static
+bool SessionManager::HasBrowserRestarted() {
+#if defined(OS_CHROMEOS)
+  CommandLine* command_line = CommandLine::ForCurrentProcess();
+  return base::SysInfo::IsRunningOnChromeOS() &&
+         command_line->HasSwitch(chromeos::switches::kLoginUser);
+#else
+  return false;
+#endif
+}
+
 SessionManagerDelegate::SessionManagerDelegate() : session_manager_(NULL) {
 }
 
 SessionManagerDelegate::~SessionManagerDelegate() {
 }
 
 void SessionManagerDelegate::SetSessionManager(
     session_manager::SessionManager* session_manager) {
   session_manager_ = session_manager;
 }
 
 }  // namespace session_manager