Fix a bug that unmounting devices on the policy update can be a busy loop.

chrome/browser/chromeos/file_manager/volume_manager.h

 // Copyright 2013 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.
 
 #ifndef CHROME_BROWSER_CHROMEOS_FILE_MANAGER_VOLUME_MANAGER_H_
 #define CHROME_BROWSER_CHROMEOS_FILE_MANAGER_VOLUME_MANAGER_H_
 
 #include <map>
 #include <memory>
 #include <string>
@@ skipping 283 matching lines @@
 
   SnapshotManager* snapshot_manager() { return snapshot_manager_.get(); }
 
  private:
   void OnDiskMountManagerRefreshed(bool success);
   void OnStorageMonitorInitialized();
   void DoMountEvent(chromeos::MountError error_code,
                     const linked_ptr<Volume>& volume);
   void DoUnmountEvent(chromeos::MountError error_code,
                       const linked_ptr<Volume>& volume);
+  void OnExternalStorageDisabledChangedUnmountCallback(
+      chromeos::MountError error_code);
 
   Profile* profile_;
   drive::DriveIntegrationService* drive_integration_service_;  // Not owned.
   chromeos::disks::DiskMountManager* disk_mount_manager_;      // Not owned.
   PrefChangeRegistrar pref_change_registrar_;
   base::ObserverList<VolumeManagerObserver> observers_;
   chromeos::file_system_provider::Service*
       file_system_provider_service_;  // Not owned by this class.
   GetMtpStorageInfoCallback get_mtp_storage_info_callback_;
   std::map<std::string, linked_ptr<Volume>> mounted_volumes_;
   std::unique_ptr<SnapshotManager> snapshot_manager_;
 
   // Note: This should remain the last member so it'll be destroyed and
   // invalidate its weak pointers before any other members are destroyed.
   base::WeakPtrFactory<VolumeManager> weak_ptr_factory_;
   DISALLOW_COPY_AND_ASSIGN(VolumeManager);
 };
 
 }  // namespace file_manager
 
 #endif  // CHROME_BROWSER_CHROMEOS_FILE_MANAGER_VOLUME_MANAGER_H_