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

chrome/browser/chromeos/drive/file_system.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/chromeos/drive/file_system.h"
 
 #include "base/bind.h"
 #include "base/files/file_util.h"
 #include "base/prefs/pref_service.h"
 #include "chrome/browser/chromeos/drive/change_list_loader.h"
@@ skipping 14 matching lines @@
 #include "chrome/browser/chromeos/drive/file_system/touch_operation.h"
 #include "chrome/browser/chromeos/drive/file_system/truncate_operation.h"
 #include "chrome/browser/chromeos/drive/file_system_observer.h"
 #include "chrome/browser/chromeos/drive/file_system_util.h"
 #include "chrome/browser/chromeos/drive/job_scheduler.h"
 #include "chrome/browser/chromeos/drive/remove_stale_cache_files.h"
 #include "chrome/browser/chromeos/drive/resource_entry_conversion.h"
 #include "chrome/browser/chromeos/drive/search_metadata.h"
 #include "chrome/browser/chromeos/drive/sync_client.h"
 #include "chrome/common/pref_names.h"
+#include "components/user_manager/user_id.h"
 #include "content/public/browser/browser_thread.h"
 #include "google_apis/drive/drive_api_parser.h"
 
 using content::BrowserThread;
 
 namespace drive {
 namespace {
 
 // Gets a ResourceEntry from the metadata, and overwrites its file info when the
 // cached file is dirty.
@@ skipping 909 matching lines @@
   base::PostTaskAndReplyWithResult(
       blocking_task_runner_.get(),
       FROM_HERE,
       base::Bind(&internal::FileCache::MarkAsUnmounted,
                  base::Unretained(cache_),
                  cache_file_path),
       callback);
 }
 
 void FileSystem::AddPermission(const base::FilePath& drive_file_path,
-                               const std::string& email,
+                               const user_manager::UserID& user_id,
                                google_apis::drive::PermissionRole role,
                                const FileOperationCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   DCHECK(!callback.is_null());
 
   // Resolve the resource id.
   ResourceEntry* const entry = new ResourceEntry;
   base::PostTaskAndReplyWithResult(
       blocking_task_runner_.get(),
       FROM_HERE,
       base::Bind(&internal::ResourceMetadata::GetResourceEntryByPath,
                  base::Unretained(resource_metadata_),
                  drive_file_path,
                  entry),
       base::Bind(&FileSystem::AddPermissionAfterGetResourceEntry,
                  weak_ptr_factory_.GetWeakPtr(),
-                 email,
+                 user_id,
                  role,
                  callback,
                  base::Owned(entry)));
 }
 
 void FileSystem::AddPermissionAfterGetResourceEntry(
-    const std::string& email,
+    const user_manager::UserID& user_id,
     google_apis::drive::PermissionRole role,
     const FileOperationCallback& callback,
     ResourceEntry* entry,
     FileError error) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   if (error != FILE_ERROR_OK) {
     callback.Run(error);
     return;
   }
 
   scheduler_->AddPermission(
       entry->resource_id(),
-      email,
+      user_id,
       role,
       base::Bind(&RunFileOperationCallbackAsEntryActionCallback, callback));
 }
 
 void FileSystem::SetProperty(
     const base::FilePath& drive_file_path,
     google_apis::drive::Property::Visibility visibility,
     const std::string& key,
     const std::string& value,
     const FileOperationCallback& callback) {
@@ skipping 36 matching lines @@
     int64 num_bytes,
     const FreeDiskSpaceCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   DCHECK(!callback.is_null());
   base::PostTaskAndReplyWithResult(
       blocking_task_runner_.get(), FROM_HERE,
       base::Bind(&FreeDiskSpaceIfNeededForOnBlockingPool, cache_, num_bytes),
       callback);
 }
 }  // namespace drive