Revert 175073 because it fails to compile on Linux.

chrome/browser/media_gallery/linux/mtp_device_operations_utils.h

 // 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.
 
 // MTPDeviceOperationsUtils provides support to media transfer protocol device
 // file operation worker classes.
 
 #ifndef CHROME_BROWSER_MEDIA_GALLERY_LINUX_MTP_DEVICE_OPERATIONS_UTILS_H_
 #define CHROME_BROWSER_MEDIA_GALLERY_LINUX_MTP_DEVICE_OPERATIONS_UTILS_H_
 
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/sequenced_task_runner.h"
 #include "base/sequenced_task_runner_helpers.h"
 #include "base/threading/sequenced_worker_pool.h"
 
-namespace device {
+namespace chrome {
+
 class MediaTransferProtocolManager;
-}
-
-namespace chrome {
 
 // Helper struct to delete worker objects on |media_task_runner_| thread.
 template <typename WORKER> struct WorkerDeleter {
   static void Destruct(const WORKER* worker) {
     if (!worker->media_task_runner()->RunsTasksOnCurrentThread()) {
       worker->media_task_runner()->DeleteSoon(FROM_HERE, worker);
       return;
     }
     delete worker;
   }
 };
 
 // Returns MediaTransferProtocolManager instance on success or NULL on failure.
-device::MediaTransferProtocolManager* GetMediaTransferProtocolManager();
+MediaTransferProtocolManager* GetMediaTransferProtocolManager();
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_MEDIA_GALLERY_LINUX_MTP_DEVICE_OPERATIONS_UTILS_H_