ash: Fix system tray avatar not updated regression

ash/common/system/user/tray_user.h

 // Copyright (c) 2012 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_COMMON_SYSTEM_USER_TRAY_USER_H_
 #define ASH_COMMON_SYSTEM_USER_TRAY_USER_H_
 
 #include "ash/ash_export.h"
+#include "ash/common/session/session_state_observer.h"
 #include "ash/common/system/tray/system_tray_item.h"
-#include "ash/common/system/user/user_observer.h"
 #include "ash/public/cpp/session_types.h"
 #include "base/macros.h"
 
 namespace gfx {
 class Rect;
 class Size;
 }
 
 namespace views {
 class Label;
 }
 
 namespace ash {
 
 namespace tray {
 class RoundedImageView;
 class UserView;
 }
 
-class ASH_EXPORT TrayUser : public SystemTrayItem, public UserObserver {
+class ASH_EXPORT TrayUser : public SystemTrayItem, public SessionStateObserver {
  public:
   // The given |index| is the user index in a multi profile scenario. Index #0
   // is the active user, the other indices are other logged in users (if there
   // are any). Depending on the multi user mode, there will be either one (index
   // #0) or all users be visible in the system tray.
   TrayUser(SystemTray* system_tray, UserIndex index);
   ~TrayUser() override;
 
   // Allows unit tests to see if the item was created.
   enum TestState {
@@ skipping 20 matching lines @@
 
  private:
   // Overridden from SystemTrayItem.
   views::View* CreateTrayView(LoginStatus status) override;
   views::View* CreateDefaultView(LoginStatus status) override;
   void DestroyTrayView() override;
   void DestroyDefaultView() override;
   void UpdateAfterLoginStatusChange(LoginStatus status) override;
   void UpdateAfterShelfAlignmentChange(ShelfAlignment alignment) override;
 
-  // Overridden from UserObserver.
-  void OnUserUpdate() override;
-  void OnUserAddedToSession() override;
+  // Overridden from SessionStateObserver.
+  void ActiveUserChanged(const AccountId& account_id) override;
+  void UserAddedToSession(const AccountId& account_id) override;
+  void UserSessionUpdated(const AccountId& account_id) override;
 
   void UpdateAvatarImage(LoginStatus status);
 
   // Updates the layout of this item.
   void UpdateLayoutOfItem();
 
+  ScopedSessionStateObserver scoped_session_observer_;
+
   // The user index to use.
-  UserIndex user_index_;
+  const UserIndex user_index_;

[James Cook, 2017/03/29 00:51:23]

Hooray for const!

 
-  tray::UserView* user_;
+  tray::UserView* user_ = nullptr;
 
   // View that contains label and/or avatar.
-  views::View* layout_view_;
-  tray::RoundedImageView* avatar_;
-  views::Label* label_;
+  views::View* layout_view_ = nullptr;
+  tray::RoundedImageView* avatar_ = nullptr;
+  views::Label* label_ = nullptr;
 
   DISALLOW_COPY_AND_ASSIGN(TrayUser);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_USER_TRAY_USER_H_