cros: Clean up SessionStateDelegate refs in Chrome

components/user_manager/user_manager.cc

Index: components/user_manager/user_manager.cc
diff --git a/components/user_manager/user_manager.cc b/components/user_manager/user_manager.cc
index 22b33c0ae9196aeecc602c0c2e660a0016f29a54..a4f4282594df560994bae6e73a7e0e8851ca5d67 100644
--- a/components/user_manager/user_manager.cc
+++ b/components/user_manager/user_manager.cc
@@ -92,4 +92,16 @@ UserManager* UserManager::SetForTesting(UserManager* user_manager) {
   return previous_instance;
 }
 
+ScopedUserSessionStateObserver::ScopedUserSessionStateObserver(
+    UserManager::UserSessionStateObserver* observer)
+    : observer_(observer) {
+  if (UserManager::IsInitialized())
+    UserManager::Get()->AddSessionStateObserver(observer_);
+}
+
+ScopedUserSessionStateObserver::~ScopedUserSessionStateObserver() {
+  if (UserManager::IsInitialized())
+    UserManager::Get()->RemoveSessionStateObserver(observer_);
+}
+
 }  // namespace user_manager