We should use UserID object to identify users instead of username.

chrome/browser/browsing_data/browsing_data_remover.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/browser/browsing_data/browsing_data_remover.h"
 
 #include <map>
 #include <set>
 #include <string>
 
@@ skipping 685 matching lines @@
 #if defined(OS_CHROMEOS)
     // On Chrome OS, also delete any content protection platform keys.
     const user_manager::User* user =
         chromeos::ProfileHelper::Get()->GetUserByProfile(profile_);
     if (!user) {
       LOG(WARNING) << "Failed to find user for current profile.";
     } else {
       chromeos::DBusThreadManager::Get()->GetCryptohomeClient()->
           TpmAttestationDeleteKeys(
               chromeos::attestation::KEY_USER,
-              user->email(),
+              user->GetUserID(),
               chromeos::attestation::kContentProtectionKeyPrefix,
               base::Bind(&BrowsingDataRemover::OnClearPlatformKeys,
                          base::Unretained(this)));
       waiting_for_clear_platform_keys_ = true;
     }
 #endif
   }
 #endif
 
   // Remove omnibox zero-suggest cache results.
@@ skipping 373 matching lines @@
   waiting_for_clear_domain_reliability_monitor_ = false;
   NotifyAndDeleteIfDone();
 }
 
 // static
 BrowsingDataRemover::CallbackSubscription
     BrowsingDataRemover::RegisterOnBrowsingDataRemovedCallback(
         const BrowsingDataRemover::Callback& callback) {
   return GetOnBrowsingDataRemovedCallbacks()->Add(callback);
 }