Minimized windows should not be activated by another user in multiprofile scenario.

chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc

 // 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 "chrome/browser/ui/ash/chrome_shell_delegate.h"
 
 #include "ash/accelerators/magnifier_key_scroller.h"
 #include "ash/accelerators/spoken_feedback_toggler.h"
 #include "ash/accessibility_delegate.h"
 #include "ash/wm/mru_window_tracker.h"
@@ skipping 24 matching lines @@
 #include "chrome/grit/generated_resources.h"
 #include "chromeos/chromeos_switches.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/user_metrics.h"
 #include "ui/aura/window.h"
 #include "ui/base/ime/chromeos/input_method_manager.h"
 #include "ui/base/l10n/l10n_util.h"
 
 namespace {
 
-void InitAfterSessionStart() {
+void InitAfterSessionStart(bool is_first_run) {

[Mr4D (OOO till 08-26), 2015/04/14 20:06:55]

You can remove this.

+  if (!is_first_run)
+    return;
+
   // Restore focus after the user session is started.  It's needed because some
   // windows can be opened in background while login UI is still active because
   // we currently restore browser windows before login UI is deleted.
   ash::Shell* shell = ash::Shell::GetInstance();
   ash::MruWindowTracker::WindowList mru_list =
       shell->mru_window_tracker()->BuildMruWindowList();
   if (!mru_list.empty())
     mru_list.front()->Focus();
 
   // Enable magnifier scroll keys as there may be no mouse cursor in kiosk mode.
@@ skipping 199 matching lines @@
       Profile* profile = content::Details<Profile>(details).ptr();
       if (!chromeos::ProfileHelper::IsSigninProfile(profile) &&
           !profile->IsGuestSession() && !profile->IsSupervised()) {
         // Start the error notifier services to show auth/sync notifications.
         SigninErrorNotifierFactory::GetForProfile(profile);
         SyncErrorNotifierFactory::GetForProfile(profile);
       }
       ash::Shell::GetInstance()->OnLoginUserProfilePrepared();
       break;
     }
     case chrome::NOTIFICATION_SESSION_STARTED:

[Mr4D (OOO till 08-26), 2015/04/14 20:06:55]

Do not call this function in the first place when the variable is false.

You might want to rename it to "InitAfterFirstSessionStart" to make the fact
clearer that this is only needed to do once per system start.

Additionally you might want to add a comment like:

This should only be call once upon system start.

-      InitAfterSessionStart();
+      InitAfterSessionStart(is_first_run_);

[Mr4D (OOO till 08-26), 2015/04/14 20:06:55]

You don't even need is_first_run_ by using:

      if (user_manager::UserManager::Get()->GetLoggedInUsers().size() < 2) {
        InitAfterFirstSessionStart();
      }

+      is_first_run_ = false;
       ash::Shell::GetInstance()->ShowShelf();
       break;
     default:
       NOTREACHED() << "Unexpected notification " << type;
   }
 }
 
 void ChromeShellDelegate::PlatformInit() {
   registrar_.Add(this,
                  chrome::NOTIFICATION_LOGIN_USER_PROFILE_PREPARED,
                  content::NotificationService::AllSources());
   registrar_.Add(this,
                  chrome::NOTIFICATION_SESSION_STARTED,
                  content::NotificationService::AllSources());
 }