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

chrome/test/base/testing_profile_manager.cc

Index: chrome/test/base/testing_profile_manager.cc
diff --git a/chrome/test/base/testing_profile_manager.cc b/chrome/test/base/testing_profile_manager.cc
index cd3eb5d31884c28c154035e616a4dd4ace359bde..3c9be5d78005dab00198c7d1ef26b46058ba8572 100644
--- a/chrome/test/base/testing_profile_manager.cc
+++ b/chrome/test/base/testing_profile_manager.cc
@@ -14,6 +14,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 
 const std::string kGuestProfileName = "Guest";
+const std::string kUserManagerProfileName = "UserManager";
 
 namespace testing {
 
@@ -125,27 +126,42 @@ TestingProfile* TestingProfileManager::CreateGuestProfile() {
   return profile;
 }
 
+TestingProfile* TestingProfileManager::CreateUserManagerProfile() {
+  DCHECK(called_set_up_);
+
+  // Create the profile and register it.
+  TestingProfile::Builder builder;
+  builder.SetGuestSession();
+  builder.SetPath(ProfileManager::GetUserManagerProfilePath());
+
+  // Add the profile to the profile manager, but not to the info cache.
+  TestingProfile* profile = builder.Build().release();
+  profile->set_profile_name(kUserManagerProfileName);
+  profile_manager_->AddProfile(profile);  // Takes ownership.
+  testing_profiles_.insert(std::make_pair(kUserManagerProfileName, profile));
+
+  return profile;
+}
+
 void TestingProfileManager::DeleteTestingProfile(const std::string& name) {
   DCHECK(called_set_up_);
 
   TestingProfilesMap::iterator it = testing_profiles_.find(name);
   DCHECK(it != testing_profiles_.end());
-
   TestingProfile* profile = it->second;
 
-  ProfileInfoCache& cache = profile_manager_->GetProfileInfoCache();
-  cache.DeleteProfileFromCache(profile->GetPath());
-
-  profile_manager_->profiles_info_.erase(profile->GetPath());
+  DeleteProfileWithPath(profile->GetPath());
 }
 
-void TestingProfileManager::DeleteGuestProfile() {
+void TestingProfileManager::DeleteProfileWithPath(const base::FilePath& path) {
   DCHECK(called_set_up_);
 
-  TestingProfilesMap::iterator it = testing_profiles_.find(kGuestProfileName);
-  DCHECK(it != testing_profiles_.end());
+  ProfileInfoCache& cache = profile_manager_->GetProfileInfoCache();
+  if (cache.GetIndexOfProfileWithPath(path) != std::string::npos) {
+    cache.DeleteProfileFromCache(path);
+  }
 
-  profile_manager_->profiles_info_.erase(ProfileManager::GetGuestProfilePath());
+  profile_manager_->profiles_info_.erase(path);
 }
 
 void TestingProfileManager::DeleteProfileInfoCache() {