ChromeOS cryptohome should be able to use gaia id as user identifier.

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 70 matching lines @@
 #include "chrome/browser/android/webapps/webapp_registry.h"
 #include "chrome/browser/precache/precache_manager_factory.h"
 #include "components/offline_pages/offline_page_feature.h"
 #include "components/offline_pages/offline_page_model.h"
 #include "components/precache/content/precache_manager.h"
 #endif
 
 #if defined(OS_CHROMEOS)
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
 #include "chromeos/attestation/attestation_constants.h"
+#include "chromeos/cryptohome/cryptohome_parameters.h"
 #include "chromeos/dbus/cryptohome_client.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "components/user_manager/user.h"
 #endif
 
 #if defined(ENABLE_EXTENSIONS)
 #include "chrome/browser/extensions/activity_log/activity_log.h"
 #include "extensions/browser/extension_prefs.h"
 #endif
 
@@ skipping 744 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(),
+              chromeos::attestation::KEY_USER,
+              cryptohome::Identification(user->GetAccountId()).id(),

[Darren Krahn, 2016/02/17 20:48:05]

Moving cryptohome::Identification to chromeos/dbus would allow this to work
without the .id(), correct?

[Alexander Alekseev, 2016/02/18 13:45:14]

Yes.

               chromeos::attestation::kContentProtectionKeyPrefix,
               base::Bind(&BrowsingDataRemover::OnClearPlatformKeys,
                          weak_ptr_factory_.GetWeakPtr()));
       waiting_for_clear_platform_keys_ = true;
     }
 #endif
   }
 #endif
 
   // Remove omnibox zero-suggest cache results.
@@ skipping 322 matching lines @@
   waiting_for_clear_domain_reliability_monitor_ = false;
   NotifyIfDone();
 }
 
 // static
 BrowsingDataRemover::CallbackSubscription
     BrowsingDataRemover::RegisterOnBrowsingDataRemovedCallback(
         const BrowsingDataRemover::Callback& callback) {
   return GetOnBrowsingDataRemovedCallbacks()->Add(callback);
 }