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/string_split.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 110 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();
-  mtp_manager->AddObserver(this);
-  EnumerateStorages();
+  // May be null in unit tests.
+  if (mtp_manager) {

[Lei Zhang, 2013/02/28 02:14:43]

As is, |mtp_manager| is always true here, because
MediaTransferProtocolDeviceObserverLinux and MediaTransferProtocolManager are
both only instanciated under the same condition.

Perhaps MediaTransferProtocolManager should be owned by
RemovableDeviceNotifications as well. MediaTransferProtocolDeviceObserverLinux
can take a MediaTransferProtocolManager in the ctor instead? We can probably get
rid of MediaTransferProtocolManager::GetInstance() and have clearer ownership.

[Greg Billock, 2013/02/28 22:35:37]

That sounds like a great option. I'll add that to this change.

+    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());
@@ skipping 89 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