CleanUp: Introduce UserInfo. Move session_state stuff to ash/session.

ash/session/session_state_observer.cc

Index: ash/session/session_state_observer.cc
diff --git a/ash/session/session_state_observer.cc b/ash/session/session_state_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..48c994eaacef8ba21aa0e1986a105ef5fc086ce0
--- /dev/null
+++ b/ash/session/session_state_observer.cc
@@ -0,0 +1,25 @@
+// Copyright 2013 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 "ash/session/session_state_observer.h"
+
+#include "ash/session/session_state_delegate.h"
+#include "ash/shell.h"
+
+namespace ash {
+
+ScopedSessionStateObserver::ScopedSessionStateObserver(
+    ash::SessionStateObserver* observer)
+    : observer_(observer) {
+  ash::Shell::GetInstance()->session_state_delegate()->AddSessionStateObserver(
+      observer_);
+}
+
+ScopedSessionStateObserver::~ScopedSessionStateObserver() {
+  ash::Shell::GetInstance()
+      ->session_state_delegate()
+      ->RemoveSessionStateObserver(observer_);
+}
+
+}  // namespace ash