Revert 175073 because it fails to compile on Linux.

chrome/browser/media_gallery/linux/mtp_device_operations_utils.h

Index: chrome/browser/media_gallery/linux/mtp_device_operations_utils.h
===================================================================
--- chrome/browser/media_gallery/linux/mtp_device_operations_utils.h	(revision 175074)
+++ chrome/browser/media_gallery/linux/mtp_device_operations_utils.h	(working copy)
@@ -14,12 +14,10 @@
 #include "base/sequenced_task_runner_helpers.h"
 #include "base/threading/sequenced_worker_pool.h"
 
-namespace device {
-class MediaTransferProtocolManager;
-}
-
 namespace chrome {
 
+class MediaTransferProtocolManager;
+
 // Helper struct to delete worker objects on |media_task_runner_| thread.
 template <typename WORKER> struct WorkerDeleter {
   static void Destruct(const WORKER* worker) {
@@ -32,7 +30,7 @@
 };
 
 // Returns MediaTransferProtocolManager instance on success or NULL on failure.
-device::MediaTransferProtocolManager* GetMediaTransferProtocolManager();
+MediaTransferProtocolManager* GetMediaTransferProtocolManager();
 
 }  // namespace chrome