Regularize ownerships and lifecycle for storage monitor platform classes.

chrome/browser/storage_monitor/media_transfer_protocol_device_observer_linux.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/storage_monitor/media_transfer_protocol_device_observer_linux.h"
 
 #include "base/files/file_path.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
@@ skipping 109 matching lines @@
 }  // namespace
 
 MediaTransferProtocolDeviceObserverLinux::
 MediaTransferProtocolDeviceObserverLinux()
     : get_storage_info_func_(&GetStorageInfo) {
   DCHECK(!g_mtp_device_observer);
   g_mtp_device_observer = this;
 
   device::MediaTransferProtocolManager* mtp_manager =
       device::MediaTransferProtocolManager::GetInstance();
+  DCHECK(mtp_manager);
   mtp_manager->AddObserver(this);
   EnumerateStorages();
 }
 
 // This constructor is only used by unit tests.
 MediaTransferProtocolDeviceObserverLinux::
 MediaTransferProtocolDeviceObserverLinux(
     GetStorageInfoFunc get_storage_info_func)
     : get_storage_info_func_(get_storage_info_func),
       notifications_(NULL) {
-  // In unit tests, we don't have a media transfer protocol manager.
-  DCHECK(!device::MediaTransferProtocolManager::GetInstance());
   DCHECK(!g_mtp_device_observer);
   g_mtp_device_observer = this;
 }
 
 MediaTransferProtocolDeviceObserverLinux::
 ~MediaTransferProtocolDeviceObserverLinux() {
   DCHECK_EQ(this, g_mtp_device_observer);
   g_mtp_device_observer = NULL;
 
   device::MediaTransferProtocolManager* mtp_manager =
@@ skipping 79 matching lines @@
   device::MediaTransferProtocolManager* mtp_manager =
       device::MediaTransferProtocolManager::GetInstance();
   StorageList storages = mtp_manager->GetStorages();
   for (StorageList::const_iterator storage_iter = storages.begin();
        storage_iter != storages.end(); ++storage_iter) {
     StorageChanged(true, *storage_iter);
   }
 }
 
 }  // namespace chrome