The User Manager should be backed by a special profile, not the guest one.

chrome/common/chrome_constants.cc

 // 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/common/chrome_constants.h"
 
 #include "base/files/file_path.h"
 
 #define FPL FILE_PATH_LITERAL
 
@@ skipping 125 matching lines @@
 #if defined(OS_WIN)
 const base::FilePath::CharType kMetroDriverDll[] = FPL("metro_driver.dll");
 const wchar_t kStatusTrayWindowClass[] = L"Chrome_StatusTrayWindow";
 #endif  // defined(OS_WIN)
 
 const wchar_t kCrashReportLog[] = L"Reported Crashes.txt";
 const wchar_t kTestingInterfaceDLL[] = L"testing_interface.dll";
 const char    kInitialProfile[] = "Default";
 const char    kMultiProfileDirPrefix[] = "Profile ";
 const base::FilePath::CharType kGuestProfileDir[] = FPL("Guest Profile");
+const base::FilePath::CharType kUserManagerProfileDir[] =
+    FPL("UserManager Profile");
 const wchar_t kBrowserResourcesDll[] = L"chrome.dll";
 
 // filenames
 #if defined(OS_ANDROID)
 const base::FilePath::CharType kAndroidCacheFilename[] = FPL("AndroidCache");
 #endif
 const base::FilePath::CharType kArchivedHistoryFilename[] =
     FPL("Archived History");
 const base::FilePath::CharType kCacheDirname[] = FPL("Cache");
 const base::FilePath::CharType kCookieFilename[] = FPL("Cookies");
@@ skipping 112 matching lines @@
 const char kApplicationClientIDStringForAVScanning[] =
     "2676A9A2-D919-4FEE-9187-152100393AB2";
 
 #if defined(OS_ANDROID)
 const size_t kMaxMetaTagAttributeLength = 2000;
 #endif
 
 }  // namespace chrome
 
 #undef FPL