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

chrome/browser/extensions/extension_assets_manager_chromeos.cc

 // Copyright (c) 2014 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/extensions/extension_assets_manager_chromeos.h"
 
 #include <map>
 #include <vector>
 
 #include "base/command_line.h"
@@ skipping 262 matching lines @@
 // static
 void ExtensionAssetsManagerChromeOS::CheckSharedExtension(
     const std::string& id,
     const std::string& version,
     const base::FilePath& unpacked_extension_root,
     const base::FilePath& local_install_dir,
     Profile* profile,
     InstallExtensionCallback callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
-  const std::string& user_id = profile->GetProfileUserName();
+  const user_manager::User* user = chromeos::ProfileHelper::Get()->GetUserByProfile(profile);
   user_manager::UserManager* user_manager = user_manager::UserManager::Get();
   if (!user_manager) {
     NOTREACHED();
     return;
   }
 
-  if (user_manager->IsUserNonCryptohomeDataEphemeral(user_id) ||
+  if (user_manager->IsUserNonCryptohomeDataEphemeral(user->GetUserID()) ||
       !user_manager->IsLoggedInAsUserWithGaiaAccount()) {
     // Don't cache anything in shared location for ephemeral user or special
     // user types.
     ExtensionAssetsManagerChromeOS::GetFileTaskRunner(profile)->PostTask(
         FROM_HERE,
         base::Bind(&ExtensionAssetsManagerChromeOS::InstallLocalExtension,
                    id,
                    version,
                    unpacked_extension_root,
                    local_install_dir,
@@ skipping 10 matching lines @@
   if (shared_extensions->GetDictionary(id, &extension_info) &&
       extension_info->GetDictionaryWithoutPathExpansion(
           version, &version_info) &&
       version_info->GetString(kSharedExtensionPath, &shared_path) &&
       version_info->GetList(kSharedExtensionUsers, &users)) {
     // This extension version already in shared location.
     size_t users_size = users->GetSize();
     bool user_found = false;
     for (size_t i = 0; i < users_size; i++) {
       std::string temp;
-      if (users->GetString(i, &temp) && temp == user_id) {
+      if (users->GetString(i, &temp) && temp == user->GetUserID().GetUserEmail()) {
         // Re-installation for the same user.
         user_found = true;
         break;
       }
     }
     if (!user_found)
-      users->AppendString(user_id);
+      users->AppendString(user->GetUserID().GetUserEmail());
 
     // unpacked_extension_root will be deleted by CrxInstaller.
     ExtensionAssetsManagerChromeOS::GetFileTaskRunner(profile)->PostTask(
         FROM_HERE,
         base::Bind(callback, base::FilePath(shared_path)));
   } else {
     // Desired version is not found in shared location.
     ExtensionAssetsManagerHelper* helper =
         ExtensionAssetsManagerHelper::GetInstance();
     if (helper->RecordSharedInstall(id, version, unpacked_extension_root,
@@ skipping 179 matching lines @@
     if (!extension_info->GetDictionaryWithoutPathExpansion(*it,
                                                            &version_info) ||
         !version_info->GetList(kSharedExtensionUsers, &users) ||
         !version_info->GetString(kSharedExtensionPath, &shared_path)) {
       NOTREACHED();
       return false;
     }
 
     size_t num_users = users->GetSize();
     for (size_t i = 0; i < num_users; i++) {
-      std::string user_id;
-      if (!users->GetString(i, &user_id)) {
+      std::string user_email;
+      if (!users->GetString(i, &user_email)) {
         NOTREACHED();
         return false;
       }
+      const user_manager::UserID user_id(std::string() /* gaia_id */, user_email);
       const user_manager::User* user = user_manager->FindUser(user_id);
       bool not_used = false;
       if (!user) {
         not_used = true;
       } else if (user->is_logged_in()) {
         // For logged in user also check that this path is actually used as
         // installed extension or as delayed install.
         Profile* profile =
             chromeos::ProfileHelper::Get()->GetProfileByUserUnsafe(user);
         ExtensionPrefs* extension_prefs = ExtensionPrefs::Get(profile);
@@ skipping 23 matching lines @@
           std::make_pair(id, base::FilePath(shared_path)));
     } else {
       extension_info->RemoveWithoutPathExpansion(*it, NULL);
     }
   }
 
   return true;
 }
 
 }  // namespace extensions