Add SessionStateObserver with ActiveUserChanged()

ash/test/test_session_state_delegate.cc

 // Copyright (c) 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/test/test_session_state_delegate.h"
 
 #include "base/string16.h"
 #include "base/utf_string_conversions.h"
 
 namespace ash {
@@ skipping 77 matching lines @@
   return null_image_;
 }
 
 void TestSessionStateDelegate::GetLoggedInUsers(UserEmailList* users) {
 }
 
 void TestSessionStateDelegate::SwitchActiveUser(const std::string& email) {
   activated_user_ = email;
 }
 
+void TestSessionStateDelegate::AddSessionStateObserver(
+    ash::SessionStateObserver* observer) {
+}
+
+void TestSessionStateDelegate::RemoveSessionStateObserver(
+    ash::SessionStateObserver* observer) {
+}
 
 }  // namespace test
 }  // namespace ash