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

chrome/browser/chromeos/login/user_manager.cc

Index: chrome/browser/chromeos/login/user_manager.cc
diff --git a/chrome/browser/chromeos/login/user_manager.cc b/chrome/browser/chromeos/login/user_manager.cc
index 4762bd07f595d49960b7ba5819f4b394878a1aab..d460086cdcb98d4187545b2f72dd37d6e09aabe1 100644
--- a/chrome/browser/chromeos/login/user_manager.cc
+++ b/chrome/browser/chromeos/login/user_manager.cc
@@ -13,6 +13,7 @@ namespace chromeos {
 
 // static
 const char UserManager::kLoggedInUsers[] = "LoggedInUsers";
+const char UserManager::kUserWallpapers[] = "UserWallpapers";
 const char UserManager::kUserImages[] = "UserImages";
 const char UserManager::kUserDisplayEmail[] = "UserDisplayEmail";
 const char UserManager::kUserOAuthTokenStatus[] = "OAuthTokenStatus";
@@ -69,6 +70,8 @@ void UserManager::Set(UserManager* mock) {
 // static
 void UserManager::RegisterPrefs(PrefService* local_state) {
   local_state->RegisterListPref(kLoggedInUsers, PrefService::UNSYNCABLE_PREF);
+  local_state->RegisterDictionaryPref(kUserWallpapers,
+                                      PrefService::UNSYNCABLE_PREF);
   local_state->RegisterDictionaryPref(kUserImages,
                                       PrefService::UNSYNCABLE_PREF);
   local_state->RegisterDictionaryPref(kUserOAuthTokenStatus,