Getting rid of GetDefaultProfile & fixing multi user issues with accessibility

ash/session_state_observer.h

 // 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.
 
 #ifndef ASH_SESSION_STATE_OBSERVER_H_
 #define ASH_SESSION_STATE_OBSERVER_H_
 
 #include <string>
 
 #include "ash/ash_export.h"
+#include "base/basictypes.h"
 
 namespace ash {
 
 class ASH_EXPORT SessionStateObserver {
  public:
   // Called when active user has changed.
   virtual void ActiveUserChanged(const std::string& user_id) {}
 
   // Called when another user gets added to the existing session.
   virtual void UserAddedToSession(const std::string& user_id) {}
 
  protected:
   virtual ~SessionStateObserver() {}
 };
 
+// A class to attach / detach an object as a session state observer with a
+// scoped pointer.
+class ASH_EXPORT ScopedSessionStateObserver {
+ public:
+  explicit ScopedSessionStateObserver(ash::SessionStateObserver* observer);
+  virtual ~ScopedSessionStateObserver();
+
+ private:
+  ash::SessionStateObserver* observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedSessionStateObserver);
+};
+
 }  // namespace ash
 
 #endif  // ASH_SESSION_STATE_OBSERVER_H_