Add SessionStateObserver with ActiveUserChanged()

ash/session_state_delegate_stub.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/session_state_delegate_stub.h"
 
 #include "ash/shell.h"
 #include "ash/shell/example_factory.h"
 #include "base/string16.h"
 #include "base/utf_string_conversions.h"
@@ skipping 45 matching lines @@
 const std::string SessionStateDelegateStub::GetUserEmail(
     MultiProfileIndex index) const {
   return "stub-user@domain.com";
 }
 
 const gfx::ImageSkia& SessionStateDelegateStub::GetUserImage(
     MultiProfileIndex index) const {
   return null_image_;
 }
 
-void SessionStateDelegateStub::GetLoggedInUsers(
-    UserEmailList* users) {
+void SessionStateDelegateStub::GetLoggedInUsers(UserIdList* users) {
 }
 
-void SessionStateDelegateStub::SwitchActiveUser(const std::string& email) {
+void SessionStateDelegateStub::SwitchActiveUser(const std::string& user_id) {
+}
+
+void SessionStateDelegateStub::AddSessionStateObserver(
+    ash::SessionStateObserver* observer) {
+}
+
+void SessionStateDelegateStub::RemoveSessionStateObserver(
+    ash::SessionStateObserver* observer) {
 }
 
 }  // namespace ash