Enable user change background image in settings page in Aura build.

chrome/browser/chromeos/background/desktop_background_observer.cc

Index: chrome/browser/chromeos/background/desktop_background_observer.cc
diff --git a/chrome/browser/chromeos/background/desktop_background_observer.cc b/chrome/browser/chromeos/background/desktop_background_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e803c609061ae7937d6a306e7a263349bcab3077
--- /dev/null
+++ b/chrome/browser/chromeos/background/desktop_background_observer.cc
@@ -0,0 +1,50 @@
+// 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.
+
+#include "chrome/browser/chromeos/background/desktop_background_observer.h"
+
+#include "ash/shell.h"
+#include "ash/desktop_background/desktop_background_controller.h"
+#include "ash/desktop_background/desktop_background_resources.h"
+#include "base/logging.h"
+#include "chrome/browser/chromeos/login/user_manager.h"
+#include "chrome/common/chrome_notification_types.h"
+#include "content/public/browser/notification_service.h"
+
+namespace chromeos {
+
+DesktopBackgroundObserver::DesktopBackgroundObserver() {
+  registrar_.Add(
+      this,
+      chrome::NOTIFICATION_LOGIN_USER_CHANGED,
+      content::NotificationService::AllSources());
+}
+
+DesktopBackgroundObserver::~DesktopBackgroundObserver() {
+}
+
+int DesktopBackgroundObserver::GetUserWallpaperIndex() {
+  chromeos::UserManager* user_manager = chromeos::UserManager::Get();
+  const chromeos::User& user = user_manager->GetLoggedInUser();
+  DCHECK(!user.email().empty());
+  int index = user_manager->GetUserWallpaper(user.email());
+  DCHECK(index >=0 && index < ash::GetWallpaperCount());
+  return index;
+}
+
+void DesktopBackgroundObserver::Observe(int type,
+    const content::NotificationSource& source,
+    const content::NotificationDetails& details) {
+  switch (type) {
+    case chrome::NOTIFICATION_LOGIN_USER_CHANGED: {
+      ash::Shell::GetInstance()->desktop_background_controller()->
+          OnDesktopBackgroundChanged(GetUserWallpaperIndex());
+      break;
+    }
+    default:
+      NOTREACHED();
+  }
+}
+
+}  // namespace chromeos